OK, the picture thing works like this.  You have to upload your pics to a server like the one squidd posted. (I have my own server)  Then, in your post on HeyMow.com, you type in the address to your picture which will be something like:
"http://www.yourphotoservername.com/path/yourpicname.jpg" no quotes
Obviously the address will be different.  A pic on my server here at the house would have the address:
http://12.218.75.234/wkakarting/1stdayonyamaha.jpg

Once you type in the address to your pic, you highlight the address (click and hold left mouse button at the end of the address and drag the pointer to the beginning of the address then let go of the mouse button)  then click the "IMG" button at the top of the post editor.

The "post" your reply and it should show the picture instead of the address.