Click on the picture until it is fullsize...
Then right click on the picture and you will see a drop down menu with the word properties at the bottom - click that.
There is no "properties button" like in some image programs but you will see the word "address" and the URL will be after it. Copy everything from http to the end where it say .jpg , .gif etc.
Go back to your post and click the IMG button and paste all that information into the box that opens.
Try it??

I probably made it too long and with things you already know - if so sorry!