Home
The home screen is where you'll see all your active task groups. To create a task group, select the task group button at the bottom left.
A new window will pop up, name this task group and save it. 
To select the task group, look for the name above the home screen icon. 
Keep in mind that you can have multiple sites selected for your task group. You are not limited to one site (but it helps with organization).
Deleting Task Group
To delete a task group, select the menu at the top left and select "Delete Task Group." 
This will also delete all tasks within the task group.