You upload your photo into photobucket by clicking the choose file button (1) then when it's done you'll see a thumbnail of your photo there underneath. Underneath it you'll see some links, in those boxes, you want the direct link (2), copy and paste that and then when you're here, click the "Img" tag above the text box when making a post, and paste the link in between the [!img] [/img] (There's no exclamation mark there I just did that so it would show up otherwise the img tag goes invisible.)
If you did it right it should look like this, minus the exclamation mark...
[!img]http://i15.photobucket.com/albums/a376/rght190/Tobogan3.gif[/img]
Which when you post looks like this