This does presume you are using the website rather than the app though; we need to right some how-to bits for the app i guess. And it doesn't explain how to attach a pic to a post rather than upload to the gallery - I will edit the above thread when i have a mo.
I think you have to have made 5 posts before it will let you upload pics at all anyway too so make a few more posts How are you using the forum, website or app? And I'll try walk you through it