To get started, go to deploy.apple.com
This is the portal that Apple uses for managing DEP, app purchases, and Apple IDs for students under 13. The setup process will involve you creating a new Apple ID just for use with the Apple Deployment Programs. This Apple ID will require you to set up two-factor authentication. Keep in mind, two factor authentication takes up to three days to be authorized. In addition, Apple can take up to a week to authorize your DEP account. Plan ahead.
Need help with two factor authentication? - http://support.apple.com/en-us/HT204152
From the page shown above, choose Enroll Now this will walk you through setting up an account. You need to be a person in your organization authorized to do this. The requirements are that you are a C level employee (CEO, CIO, etc... ) There is a list of options to choose from. If you are not, you will need the assistance of one of these people in your organization to enroll. I was not able to set up our DEP account, I needed to have our Director of Technology do it. Apple is pretty strict on this point. They will call you to verify this, they also look at your organization’s website to make sure you are listed with the proper title. In our case, they called HR to make sure our Director of Technology was who he said he was. (I think there were less hoops to jump through in getting a mortgage.)
Once you have been approved by Apple, you can login and start deploying devices. Please note: each time you login, you will be prompted to authenticate via two-factor authentication. If you are in an environment with multiple administrators, it seems the limit is five phone numbers. Once you select the appropriate number, Apple will send you a text with a four-digit PIN.