Help! Cannot figure out how to put a pic up to be on all my posts

Cindy , i will try to explain ; not sure if I can , but lets give it a try !!
I always use photo-cd's to post pics from .
First , I look up the number of the pic I wanna post.
Then I type my reply , and on the bottom I clich on the sqare dot next to where is "attach file" .
Then you typ in the number of the pic and the place to find it (photo-cd) .
And then submit !!!
good luch ; hope it works !!