Sometimes people link direct urls to the image tag, like [[Image:http://AnyDomainName.com/files/logo.jpg]] - which doesn't work, just the plain image url link works. For example http://AnyDomainName.com/files/logo.jpg.

Sizing: [[Image:Example-External.jpg|100px]]  

Or you can use the Upload file function here at AboutUs, located in the right "useful links" sidebar. This uploads the image to AboutUs, and you may now link to an internal image.

[[Image:Example.jpg]]