You can connect to any number of myOsmo accounts from any iPad.
To connect to an additional myOsmo account:
1. Return to the main menu by tapping the gear icon. (In Osmo Numbers Education, you have to swipe down until you get to the home screen.)
2. From the main menu, tap the current player's avatar button on the top right corner.
3. Tap the gear button in the bottom right corner. Then tap "Add Account".
4. You can switch between accounts by tapping your account name at the bottom of the screen.
For more information, please see our PDF guide to myOsmo.