There are three options for restarting your Xfinity Gateway:
Log in to xfinity.com/myaccount. Scroll and select Manage Internet. Select Restart Modem. Select Start Troubleshooting to begin a reset.
Open the Xfinity My Account app. Scroll and select Internet. Select your modem and then select Restart this device to being the process.
Manually restart your Gateway by unplugging the power cable, waiting a minute and plugging it back in.
If you have any issues during self-installation, feel free to contact Xfinity customer service to get help or visit their support center online.