Is this an IAP-105-US or AP-105-US.
If it's an IAP, then you should connect it to a wired uplink port, then power it up. If it's factory defaulted, then it should broadcast an SSID called "instant".
Connect to that and open up a browser ...the default credentials are admin/admin
If it's NOT factory defaulted, take a paper clip and hold down the reset button located at the bottom of the unit. Power it up with this pressed in and the power LED will flash rapidly. Once this occurs, take the paper clip out. The unit is now defaulted.