Do they have console ports? They will either be regular serial ports or RJ-45 ports marked "console"
You'll need the right serial cable to connect. Once you hook up the cable, use a terminal emulator (Hyperterminal on windows) to connect via the console.
There may still be an administrative password for access. If that's the case and you don't have any documentation, you might have to reset to default configuration and reconfigure.
