Summary
See the [http://en.wikipedia.org/wiki/Wikipedia:Picture_tutorial Picture tutorial for more in depth information] including specifying sizes alignment and captions.
To add an image you first edit the article where you want the image to appear and add the markup for an image:
This will appear as a [http://en.wikipedia.org/wiki/Wikipedia:Red_link red link]:
- ;
Click on the link to upload the image. Once it is uploaded it will be displayed in the article.