How to modify certain properties of a group
To modify a group, first go into its settings by clicking on the settings icon at the top right of the screen.
If you are a group owner, or if not, the group owner has enabled all of the permissions for you, you can choose to add new people to the group, change the name of the group, or change the category that it's stored under. You can also add or remove people from the group.
To add new users to a group, simply tap on the "+ Add People" button or select the "People" tab. In the people tab, you will see who is currently in the group.
By clicking on the icon at the top right of the screen you can add more users into the group. By clicking on an individual user who is already in the group, their name card will pop up and at the bottom of it is an option to remove the user from the group.