Here's how to add a picture:
1a. Find an image you want on your page on any other page in the wiki, or on the image list page.
1b. If you want to upload a new picture, go to the upload file page.
2. Once you've found or uploaded an image , find out its name (including the extension), which will be something like Image:Image name.
3. Now, find a nice place on your user page, edit the code, and add this text, replacing the name and caption appropriately: