I'll give it a try:
1First notice in the heading of each post there are a row of symbols, starting with the letter B, the I and continuing until you see the interlocked links, the a square icon and then a happy face.
2The square icon is what you need to first get the image loaded. You click on that icon and then drag/drop your desired image to the popup window.
Once that is done you can click post reply.
3 Then go back into the post and right click on the image and choose "copy image address"
4 Go to your signature and click edit. at the appropriate spot in your signature click on the interlocking links and then past the address you copied in #3 above. Save your signature.
Hope that works for you.