chartIT works on a tenancy basis. You will have one login (email address and password) for the chartIT app and chartIT reporting, and within that one login you will be able to access multiple tenancies/teams.
The tenancy/team you chart your data into will dictate whom your data is shared with. Every user has a personal tenancy when they subscribe which generally contains data for yourself only. From there, you can setup other tenancies which mimic different teams. If you chart data into those tenancies, all users with access to those tenancies will be able to see that data. This makes it really simple to share data with the appropriate coaches and athletes.
In conjunction with this, if you have a Gold level subscription you have the ability to export and import games of data to another Gold chartIT user. This is helpful if you have data across different tenancies that you would like to copy across or if you are friends with other users that are willing to share their game data with you.