Don't know where to put this but this is how I do it.
First off, if your screenshot is a TGA file you can either download a software to convert files for you or you can use a website like http://image.online-convert.com/convert-to-jpg
I use this software http://easy2convert-tga-to-jpg.software.informer.com/
Once the screenshot is converted it's time to get it uploaded.
Go to http://postimage.org/ upload the file and choose 640x480 (for message boards)
Pick Hotlink 1
Paste it into your text.... And taadaaa!
After all that is done go to the screenshot thread (viewtopic.php?f=6&t=1810&p=127360#p127360) and start uploading!
Good luck.