Welcome to the forums!
Installing the adapter itself is simple, whack it in the bottom of your Gamecube, then plug one end of the phone cable you got with it into the socket on the side of the adapter, and stick the other end in a Phone Socket (Adapter may be needed).
If however you mean how do you set up the game/adapter to play online PSO, click the link below to go to a thread where someone else recently asked the same thing.
Click Here to go to the thread "Modem Adapter"
Hope that helps, if not, i'd be happy to help you further!
Installing the adapter itself is simple, whack it in the bottom of your Gamecube, then plug one end of the phone cable you got with it into the socket on the side of the adapter, and stick the other end in a Phone Socket (Adapter may be needed).
If however you mean how do you set up the game/adapter to play online PSO, click the link below to go to a thread where someone else recently asked the same thing.
Click Here to go to the thread "Modem Adapter"
Hope that helps, if not, i'd be happy to help you further!