first of all..you search the address of the pic you want to post, then you go to the reply..and you see some buttons above the white space where you can type your post in. Push the IMG button, and enter the address to your pic.. your pic is posted after you pushed the Submit Reply of your post
your own pics: either you put them on some webspace where you can link to, or you can use the attachment function of this board. Beneath the white space for your post, you can see: Attach file. Click Browse and go to the pic you want to attach.
to get an URL from a pic you just rightclick on the pic, choose properties and there you'll see the address..