Make sure you submit your coaching staffs for each of your teams after you register unless you use Stack Sports websites. Stack Sports websites automatically sync their coaches and players to the PONY Datacenter.
If you don't use a Stack Sports website, once you enter them in the system or choose to bulk upload them they will be sent notification that they can create a username and password or reset their current password if they are a returning coach in your organization.
Once they create a new username/password or log in with an existing account they will have access to the teams you have assigned them to in the coach portal.