Before you invite your team, you should send them some mail to let them know that LYS is using TeamSnap and that they should expect an invitation. Let them know that the mobile app is a great tool for team coordination, and encourage them to install the app on their iPhone or Android devices.
From your team's page, select the "Roster" Tab.
Review the list of names, and click one of the "Invite to join" buttons.
By default, checkboxes will invite the whole team to join. At the bottom click "Send Invitations.