Hello,
The best way to attach an image on forum is to host it on the external server. I recommend you http://tinypic.com/. When you upload your photo, you'll get a bunch of tags and links, the second one (the one that begins from [IMG]) is made to paste it on the forum.

I don't know english-language forum but there's a group on Facebook where you will also find a help https://web.facebook.com/groups/mk1tt/?ref=group_header

Welcome