Your Masterfax ATA will arrive from CallTower preconfigured with the fax DID that you indicated was needed for the device.
The device will have several ports in the back. Plug your ethernet cable into the WAN port. Plug your fax line (phone cord) into phone port 1. Plug in the power cord to the outlet, and your Masterfax should come online and be operational for your preprogrammed fax number.