Go to your FTF gallery, and upload the pic there...then copy the bb code and paste in your thread. Or, if you go with something like photobucket, upload your pic there, then copy the IMG code, then paste in your response.
aside from the "Attach File" option on certain online forums
One needs an Internet Image Host to copy the code from for posting in a thread.
The FTF Gallery feature has such an option thus you can keep everything to do with you and this site ON THIS Site .