Turn on the answering machine by pressing the on/off button on the base. Set the time and date by pressing the Time/Set button (to the right of the menu button) and pressing Change until the correct day or time is heard. Then press Time/Set again.
To record a message, press Menu until you hear "Set Outgoing Message", then press Record and speak the message (include the mailbox info if you are using them). Press any Play/Stop button to end the message.
Set the various features by pressing Menu to access each one, then press Change to change the setting. Press Time/Set to lock in the change and press Menu to change the next feature. Press a Play/Stop key to leave the menu.
The most important one is "Set Announce Only" to Off for callers to leave a message.
All messages will go into Mailbox 1 unless the caller indicates a different mailbox. Press the Mailbox button to hear new messages if the mailbox has a mix of new and old messages. Press the button a second time to hear all messages. Skip/Quick lets you advance to the next message and Repeat/Slow will let you hear a message again.
Press Vol (up) to adjust the base speaker volume higher during playback.
In the menu, the first option lets you set the two digit security code to access the messages when you call in from another phone. When calling press # followed by 1, 2, or 3 to access the desired mailbox. Press #4 to repeat a message. #5 to skip. Press *0 to end the remote call.
For the full manual, see: http://www.vtechphones.com/vtechphones/index.cfm/support/manuals/
and scroll down to 5866.
I hope this helps.
(all this assumes the base is on (connected to power) and connected to a good phone line. Without power it will not work at all. I test phone lines for dial tone with an old corded phone.)