For T-Mobile, activation can happen directly on your iPad. First, go to settings and scroll to "Cellular Data.” Then select your carrier and follow the prompts. When selecting your plan, T-Mobile customers need a plan with a minimum of 10GB of data to be eligible. For Verizon you will need to visit My Verizon website and follow the instructions. When selecting a Verizon plan, Unlimited and Unlimited Plus are eligible.