Chat is only available in the app, you can download the app from the App Store for iOS or the Google Play Store for Android devices.
By Default, there is an All Team Members (and All Team Admins for admins) chat created for your team. As the name indicates, this is a chat for all players, parents, coaches, etc that are on the roster.
To create a new chat for groups or to an individual:
1. Press the message icon on the bottom (second from the right) and click Chat
2. Click the '+' icon to add a chat
3. Select the recipients of the chat
4. Name your group and press 'Create'
Your new group will now be visible in the chat section