Here's some more info using photobucket. Once you've uploaded your pictures, you can select one picture by left clicking on it. On the right side, you will see the "links to share photo". Move your mouse over the "IMG" block and left click once, and you will see a cloud that says "copied" appear. Your picture link is now saved to your clipboard. Now, as admin said, right click in the content of your forum post, and click "paste". If you are adding several photos, I recommend hitting return twice after each photo is pasted to leave some space between each. Picture below is what the screen will look like in photobucket. You need two tabs opened on your internet page for this to go smoothly, one tab with this site and the other with photobucket. Now get those pictures up!
