For each client, you can assign two types of agent:
a tax agent, who will work on tax returns
a BAS agent, who will work on activity statements.
Then, when you create a tax return or activity statement for that client, the assigned agent is automatically selected.
To be able to assign an agent, you first need to create an agent in MYOB Practice. Otherwise, you'll see this message in the BAS agent details section:
Click Create a BAS or tax agent first to go to the ATO agent settings page. There, you'll be able to create a tax agent or a BAS agent.