I'm no computer whiz either! When I'm writing up a full message, I just go into the attach (little paperclip) icon, that appears at the top of the typing box. Another box will pop up, asking you to attach photos. When you click on the 'attach' boxes, this will allow you to scroll through the photos that you have got stored on your computer. Choose the ones you want by clicking on them.
Hope this is somewhat (sort of) clear?! I think that somebody has written a sticky on posting photos, too! PM me, if something I'm saying makes no sense!