First you need a APC 940-0024C or APC 940-0024B Serial Cable, then you need to get a Keyspan USB to Serial adapter dongle, then you connect to the serial cable to the DB9 connector on the back of the UPS. Use Putty and Serial at 2400 baud,8n1, xon/xoff
Then you can logon using the default username and password of apc and apc. If you need to reset the passwords, press the reset button on the AP9617 unit.
See the pictorial below