A coach or player will need to register for the number of teams they wish to be rostered onto. This means they will need to either sign into their account and select Place Order or enroll from the Organization's public website. They will need to place a registration order for each individual Offering which will allow admin to roster them onto separate teams. For example, if a coach is coaching two age groups, he should place 2 orders with an enrollment in each Offering. 

Or, if you would like to register the coach or player as an Admin, follow the steps in this article: 
 https://teamsideline.zendesk.com/hc/en-us/articles/201153157-As-an-admin-how-do-I-register-or-place-an-order-for-my-customers-.