After you have registered and volunteered as the head coach...

1) Log in to your Dayton Sports Complex account
2) Click "Volunteer" in the left panel of your account homepage
3) Under your 'Volunteer Roles' click "Visit Team Page" for the team you'd like to invite players and staff
4) Click the 'Roster' tab on your team home page
5) Click the 'Manage Roster Invites' button on the right

From here you'll be able to send invitations via email to all players and staff.  You'll also be able to see which players have accepted invites and which have not.