Once you've signed up and created a Group, you can start getting your Group setup. If you haven't setup your Group yet then click here for details on what to do.
Assuming you've create your Group and you've been brought to, or logged into, the Control Panel, the next step is to setup some Sub-Groups. Sub-Groups are the groups to which you allocate your members. You can have as many Sub-Groups as you want and members can be assigned to multiple Sub-Groups, but getting the Sub-Groups set-up is really where you need to start. More information on Sub-Groups can be found here.
If you're a school, then you'll want to create a Sub-Group for each class and probably for each year. If you're a sports club, then you'll want a Sub-Group for each Team or Age Group.
To set-up a Sub-Group, click on 'Static Data' from the Main Menu of the Control Panel, and then 'Manage Sub-Groups'. From here you enter a code and the name of the Sub-Group. The code can be the same as the Name, but you can decide. Click on 'Submit' to create your Sub-Group and then go ahead and create some more.
Note that once you have created the Group, you have Admin rights with that Group.
Once that's done, you'll probably want to start inviting some members / users to join the app. Click here for more information on creating new users.