there's a couple of threads about that -

http://www.ttwebsite.com/forums/showthre...?tid=18350

http://www.ttwebsite.com/forums/showthre...st+picture

Basically, stick your pics on a hosting site (https://postimages.org/ or whatever) then use the "insert an image" box/button above (visible when you're replying) to link to it, following the instructions in the other threads to make sure it's the right size!
Hope that makes some kind of sense!