On the web:
1. Click your name in the upper right hand corner of the home screen
2. Click 'Create a new group' in the drop-down
Note: On the web, you can add people to a group by name only (no contact info required).
1. Tap to navigate to your Groups tab
2. You should see an option to "Start a group" at the bottom of your list of groups
1. Tap the more option (three vertical dots) in the top right corner of the screen
2. Choose 'Create a group'