Sandeep can help you with this better than I, at least quicker, but if you use 3389, you may want to change the port.
Unfortunately, if you use multiple computers, you have to keep forwarding the port number to the next highest number and use that after the colon. But, once set up, it is rather easy.
On your "server" go to Administrative Tools, up to Terminal Services and see if you have TS Gateway Services. If you don't have these, you probably don't have a Remote Gateway. Part of the difficulty is that Microsoft continues to changes names from RDP to RDC to Terminal Services to Remote Gateway, etc.
