Welcome to the Xfinity Forums! I'd be happy to provide assistance with changing your password. Since there were no details on which password you wanted to change (WiFi or your account password), I wanted to provide a few ways to do this that will assist you with both if needed in the future.
Xfinity xFi puts you in the driver’s seat, letting you personalize and control your WiFi experience. To manage your WiFi info:
The Xfinity My Account mobile app lets you manage your Xfinity services and account settings on the go.
To get your WiFi information on My Account using your computer, tablet, or phone:
I hope this helps.