First make sure the answering machine is on; press the On/Off button to turn it on and off. To set a message to be heard by those calling in: press and hold Skip/Annc. Begin speaking when A shows in the message window. Speak from about 9 inches away from the phone. Messages must be more than 3 seconds and less than 3 minutes long.
Press Prog/Mem and then Skip/Annc to hear the current message. Press and hold Setup until you hear the current setting (Selected announcement is A or Announce Only). Use Skip/Repeat to change the setting. No one will be able to leave a message if Announce Only is on.
After you have held the Setup button, as above, press Setup additional times to set the number of rings before the machine answers and the remote access code among other features.
To set the date and time, press and hold Clock for 1 second. Use the Skip button to advance the current digit; the Repeat button will subtract one from the current value. Press Clock again to advance to the next value to change (day of week, hour, minute, second).
Press Play to hear new messages; press and hold Play to hear all messages. Press Repeat to repeat the current message. Press Repeat twice to hear the last message. Hold Repeat to slow the message playback.
Delete a message by pressing Remove during playback; press Remove twice to delete all messages (if there are no new messages). A blinking F indicates the memory is full and messages must be deleted.
I hope this helps.
(btw additional instructions for the answering system are available at the AT&T website. Direct link: http://telephones.att.com/documents/product_Product/219/UserManual/1982/1855_manual_bkm.pdf
which may or may not work.)