Hi millie, there are some ways to do it, one is through Flickr, other is imageshack
Way one: First go to www.flickr.com and create an account there.
Next, download and install their upload manager: http://www.flickr.com/tools/
Now next time you want to post a pic open the program you installed and drag&drop the pics you want there.
When finished it'll send you to www.flickr.com
Select one of the pics and right click it, from the menu select "copy image link", that's the link you need.
Now, post a reply and press the mountain icon (next to the Youtube icon), paste the link
and that's it.
I'll try to make a visual guide
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One of God's own prototypes. Some kind of high powered mutant never even considered for mass production. Too weird to live, and too rare to die.