Here is a sticky I made on my site - It will work on all the gun forums:
First, make sure that the photo is not too HUGE.
Then, upload it to this site:
http://www.imageshack.us/
There are other similiar sites, but you do not need an account at this site.
Then, copy the exact URL of the photo.
Next, come here and put the "[IMG]" tag on the front
and "[/IMG]" tag on the rear of the picture link.
EXAMPLE: [IMG]link[/IMG]
Leave NO spaces between the link and the tags!
And, that's all there is too it