you put [img] in front of it and [/img] after it
like this [img]
http://www.hilariousgifs.com/rolling-fighter/ [/img]
but with out the spaces and you get this
[img]
http://www.hilariousgifs.com/rolling-fighter/[/img]
I tried it the other way I know and its not working for some reason on this one.
However that one has been posted but it's still funny LOL