This page explains how to manually create your own user space subpage, also known as a sandbox. Alternatively, here is your user sandbox (even if you haven't created it yet). For future easy access, you can put {{My sandbox}} on your user page.

1. Create a link to the page you want. You can do this by editing your user page and adding [[/sandbox]]; this will link to a subpage called "sandbox".
2. Click the link (which should be red, because the page does not exist yet).
3. Write something in the edit window, add an edit summary, and press Publish changes. You can press the edit button to make further changes.

A list of existing subpages can be seen using Special:Prefixindex (for example, Special:Prefixindex/User talk:Example/). You can usually have anything on a subpage that you might have on a user or user talk page, except for a few items (see below) that must be visible to other users if posted. Hierarchies of subpages are also possible. You can have as many subpages as you want but keep in mind that Wikipedia is not a free web host, please use subpages within reason. (See: Wikipedia:Subpages for more.)