First of all, you can change the port number by going to ‘Edit Options’ -> ‘Advanced’ -> ‘HTTP Port’.
Second, before you do so, please note that you should NOT set port forwarding on your tp-link adapter (in client mode) — the tp-link adapter serves as a simple pass-through and it transparent (imagine it as a wired connection except it goes wireless). The port forwarding should be set on your main router (i.e. the router connected to your cable modem).