1.You can video chat with anyone else who has Google Duo app. 

2.You can also use other video calling apps, but the person you are calling must have the same app you are using and be signed in, Tap the google Duo app.

3.Tap the new call and contact you want to video chat with.

4.Tap the 'video' icon.

5.End the video chat by tapping on the red 'phone' icon.