Typically the first step in using an image or other media file is to upload it to Wikimedia Commons, but for legal reasons, some files must be uploaded to the English Wikipedia instead. Wikipedia:Upload helps you to choose between these options.

Many media files are copyrighted without permission to redistribute, and cannot be uploaded to either location. See Wikipedia:Image use policy for details about which media files can be uploaded. If a file of the same name exists on both Wikipedia and Wikimedia Commons, the Wikipedia file will be displayed.

The preferred image formats are SVG, PNG, JPEG, and XCF. The preferred sound formats are Ogg (using FLAC, Speex, and Vorbis codecs) and MIDI. Videos must be Ogg files using the Theora video codec.

Bear in mind that media files can contain hidden data, such as comments that are not displayed, Exif metadata, and messages hidden via steganography.

Choose a good name for the media file before you upload it, as you will not be able to rename it yourself later. Once the file is uploaded you should be able to read and make sense of its file page, which describes the file and lets the reader see the image in its original size.

Be aware that for some file formats, especially animated .gif files, very high resolution images can pose a problem for performance (see this link for details). In the case of non-free files, only low-resolution images are acceptable for policy reasons. In other cases, especially for freely licensed photographs in .jpg format, upload the best quality and highest resolution version available. These images will be automatically scaled down to low-resolution thumbnails as appropriate for display in a page.

Once you have uploaded a file, you can use it in a Wikipedia article by editing the page to contain text that looks like this, with the result shown just below it and to the right:

[[File:Wikipedesketch1.png|thumb|alt=A cartoon centipede with 7 hands reads a book, lifts another, types on a laptop, and holds a bottle.|The Wikipede edits ''[[Myriapoda]]''.]]

(Although the above text may appear in multiple lines for formatting purposes, the actual text should be on one line.) The above text contains the image file name "File:Wikipedesketch1.png", the alt text "A cartoon centipede with 7 hands reads a book, lifts another, types on a laptop, and holds a bottle" and the caption as "The Wikipede edits Myriapoda." Alt text is intended for visually impaired readers or those with older browsers or computers that cannot display the image, and should describe the gist of the picture's appearance. The caption is intended for all readers and explains the picture's meaning. Alt text and captions typically have little text in common.

A reader of the article can click on the thumbnail, or on the small double-rectangle icon below it, to see the corresponding image page. The image normally floats to the right as illustrated here.

The extended image syntax provides many options to control how an image is displayed. You can make it float to the left, center it, and place it without text flowing around it. You can change its size and let the reader move around in a panorama. You can avoid image stackups in several ways, for example, by alternating left and right images, by aligning images, and if all else fails by forcing a break. You can create a gallery of images arranged into an array by using table syntax, by using a template such as {{Gallery}}, and by using a gallery tag (unfortunately, gallery tags do not support alt text, so they generate galleries that are not accessible to readers who cannot see the images). Also, you can create plain pictures that do not have captions and can be mingled with text and other images; these can use more fine-grained techniques, including borders, vertical alignment with text, and control over links. You can also link to an image without displaying it.

File names should be clear and descriptive, without being excessively long. While the image name doesn't matter much to the reader (they can reach the description page by simply clicking on the image), it matters for editors. It is helpful to other contributors and for maintenance of the encyclopedia if images have descriptive or at least readable file names. For example, "File:Skyline Frankfurt am Main.jpg" is more helpful than "File:14004096 200703230833355477800.jpg".

To avoid accidental overwriting of images or other media, very generic filenames should not be used when uploading. For example, a picture of an album cover should not be given the name "File:Cover.jpg", as sooner or later someone else will try to do the same thing and overwrite the old image. The new image will then appear wherever the old one was used – in this case, an album article would then show the wrong album cover.

Files may need to be renamed for various reasons:

1. Uploader requested
2. Change from completely meaningless names into suitable names, according to what the image displays
3. Correct misleading names into accurate ones
4. Change generic bio-names into binomial scientific names
5. Correct obvious errors in file names
6. Harmonize file names of a set of images
7. Disambiguate files with overly similar names
8. Remove pejorative, offensive or crude language that would not be appropriate in the file description

Files are renamed by moving the file page and the associated talk page. Only users with the file mover right may move files. Editors without the file mover right may request that a file be moved by adding {{rename media}} to the file description page.

{{rename media|target name.extension|reason for name change}}

This will add the file page to Category:Wikipedia files requiring renaming and a file mover will process it. The "*.extension" means the file's Filename extension. For images, this will typically be the .jpg image format, though it may also include the .gif, .tiff and other image formats amongst many others.