Save the image(s) you wish to use. Upload the image to an image hosting site such as imgur then copy the image’s url and replace ‘image url’ with it.

For forums that allow HTML:

<a href="http://www.rebootrevival.com/"><img scr="image url" /></a>

For forums that allow BBCode:

[url=http://rebootrevival.com/][img]image url[/img][/url]