first time posting a pic on here from my iPhone, but it won't let me browse to pick my screenshot from the attachment pop up 🙁 help?
OP...I'm sorry to burst your bubble but you've been beaten to the punch!
https://forums.macrumors.com/threads/543903/
You can't. You have to do it on your Mac/PC. Either email it to yourself or sync it to iPhoto, and then you can upload it to the thread.