From Hang Gliding Wiki
Basically how it's done is in two steps. First you upload an image file from the main wiki page. Then you use some special syntax to include the image on the specific wiki page you are editing.
Uploading the file:
- On the wiki home page, click the link in the bar to the left that says "Upload File"
- The form to upload a file allows you to rename the file for the wiki, regardless of what it is named on your computer. Pick a simple yet descriptive name because you're going to have to type it in later.
- Add whatever descriptive text you feel is pertinent if desired.
- Notice the examples given for how to include your file on a wiki page.
- Click upload. Remember what you named the file for the wiki... you'll need to type it in soon.
Putting it on a page:
- Click edit on the page you wish to change
- Add the custom text into the page. Examples include:
- [[File:File.jpg]] to use the full version of the file
- [[File:File.png|200px|thumb|left|alt text]] to use a 200 pixel wide rendition in a box in the left margin with 'alt text' as description
- [[Media:File.ogg]] for directly linking to the file without displaying the file
- Hit 'Save Page'
- Profit!!
There are lots of formatting options for images. For a full description go to http://www.mediawiki.org/wiki/Help:Images
Something I found helpful was to prevent the text from wrapping all around the image... in other words forcing the text to end before the image and then continue below it... add this after the image text:
<br style="clear: both" />
As I did on the camera page with the following line:
[[File:mag_mount.jpg|400px|thumb|left|mag mount]]<br style="clear: both" />