It's pretty straight forward. Do you have any complications like a dsl modem or something?
Disconnect the main phone line where it enters the junction box (box where all your house phones are connected). Connect the main phone line to the doorbell fon. Run another line from the phone out slot on doorbell fon and run it to the junction box.
Disconnect the main phone line where it enters the junction box (box where all your house phones are connected). Connect the main phone line to the doorbell fon. Run another line from the phone out slot on doorbell fon and run it to the junction box.

