To retrieve messages from another phone.

First, you have to have the remote access code. The preset code from the factory was 500. If no one has changed it, you're in luck. Otherwise, you first have to be at the base unit to change the access code to something you can use. You would press "change", then press and release "setup" until you hear "Remote access code is...", then press "repeat" or "skip" to change the first digit. Press "setup" to move to the second digit. Repeat these steps until you have a 3-digit code.

Accessing the answering system from a touch tone phone:

dial your phone #. As announcement plays, enter the remote access code. The system announces the # of messages, then beeps twice. After the 2 beeps, the system is ready to accept a command. If you just want to hear the messages in box 1, wait 4 seconds and it will play them for you. Otherwise, you really need the whole manual. I have not found any online as yet, but luckily just found mine.