Computer help: Vonage set up

Vonage set up

I'm going to be helping a friend set up vonage. However, I cant seem to figure out how it works. She has different phones throughout the apratment (but only 1 line). So if I just connect vonage to one phone, it will atuomaticly send the signal to all the other pohnes (even if they are not the same kind)? I would think that you need to plug in the vonage to where the pohne line comes into the apartmnet (which I have no idea how and where it is anyway)

Can someone shed some light here?

Thanks!!