To activate your Xfinitymobile.com activate device, you can follow these steps: Make sure your Xfinity Mobile device is fully charged and turned on. Connect your device to a Wi-Fi network. Open the Xfinity Mobile app on your device. Follow the on-screen instructions to set up your account. If prompted, enter your Xfinity account number and your account PIN. Select the phone number you want to activate and follow the prompts to complete the activation process. Once the activation is complete, you should be able to make and receive calls and use your data plan.