1. Click Reply to a Thread
2. Above the text box there are some icon tools...B I U and so on. the one with the teeny picture of a mountain is the one you need to select.
3. Enter the URL
PS
Go to GOOGLE.COM and select Images on the top left
1.Type in a descriptive term e.g. Jesus weeping
2. Double click on the picture
3. Select full size image from options on right
4. Copy the URL address from the address bar and paste it
Blessings