Carol.....I'll try. I'm a Mac Dude as well...and What I just did to post this pictures is as follows:
Starting with "Post Reply" here on the forum page.
It was in iPhoto. I selected it. Went to the bottom and chose "email". Choose the "small (240x320)" in the mail photo pop up.
It will open your image in an email page.
Click on the image and drag it to your desktop.
Go to bottom of this page under "additional Options" and hit Manage Attachments.
Click one of the four "Choose File"
Go to your desktop. Choose the picture.
Hit "Upload"
Hit "Submit Reply"
Ta Dah!
(I hope)
Let us know how it goes. "Avatar" (the little picture beside your name) Class......later.
-Geary