Requirements:
A Customer/Contract needs to exist. Please refer to Create a Customer
Also a Modem needs to be already created. Please refer to Create a Modem
Steps for adding a MTA
Go to Provisioning > Modems
Choose a existing modem and open the Edit-Page. On the right side click on the Plus-Button under "Assigned MTAs" for creating a new MTA.
Fill out all the required fields to create a new MTA.
Next Add a Phonenumber