With Photobucket, you register and you get an account. There, you can store your own photos and stuff. And they will have links and stuff for you to just paste into your forum posts. Very easy, and you can keep track of your images.
Once you get a pic uploaded to the "net" somewhere, you must use "image" tags to embed the link to that URL, like this:
Note that if you right-click on the above text, and view properties, thats actually a pic, and not text.
Also, when making a post, you don't have to type those tags, just hit the little button, above the text window, that looks like a tiny mountain against a yellow sky. The dialog box that opens will prompt you for the link. What I always do, to make it easy, is open the pic in a new window, and copy-and-paste its URL. That way, you avoid typing errors.