If you're talking about adding pictures to a post, and not your signature, then follow these steps:
1st make the picture a reasonable size to post on the board, it's aggravating to other members to have to scroll to the side to view a picture.
Save the picture and open up an internet window such as
www.photobucket.com or
www.imageshack.us, upload the picture.
Then once it has uploaded there should be a direct link you can copy and paste, or you can right click on the image and copy the image address. You have to make sure the picture is at full size and not the thumbnail though.
Then in your post, click the little yellow and grey button with the mountain on it and paste the link in the provided bar. Or you can type in
Then once you submit your post the image should show up.
Hope that helped!