Congrats on your new client! QuickBooks Online Accountant is designed to simplify the management of your firm, and a large part of this is streamlining the way your team members access your clients' books. You already seem to have a solid grasp on how to manage an individual user's access, but I'm happy to show you how to efficiently assign team members to a particular client.
Once the client is set up, it's just a few easy steps to select which team members have access:
Let me know if this helps.