Help:Images

Typically you would upload an image file to the wiki (See Help:Managing files) ...before you use the following wiki text to place the image on an article:

Syntax
The full syntax for displaying an image is: Where options can be zero or more of the following, separated by pipes: The options can be given in any order. If a given option does not match any of the other possibilities, it is assumed to be the caption text. Caption text can contain wiki links or other formatting.
 * ,, or  : Controls how the image is formatted
 * ,,  ,  : Controls the alignment of the image on the page
 * : Resizes the image to the given width in pixels

Other files
You can link to an external file using the same syntax used for linking to an external web page. Or with different text:

If it is enabled on your wiki (see Manual:$wgAllowExternalImages), you can also embed external images. To do that, simply insert the image's url:

Gallery of images
It's easy to make a gallery of thumbnails with the  tag. The syntax is:

Administration of images/files
See here: Manual:Image Administration