I use photobucket.com - a free service.
It will quickly download the photo from your computer and give you 3 codes. The [img] code is for putting the picture in your signature on your profile. It will display every time you post on a thread but only once per page. If you use the <tag> code, you can copy and paste that code right in a thread and the picture will display along with your response. This would be a one time posting.

There are also other ways of posting pictures, but this is the way I do it. Good luck!