Activation codes are intended to be used in schools as a convenient way to connect multiple devices to the same myOsmo account.
To see your activation code, please sign into your account at my.playosmo.com. The code will only be displayed if you have a school account, so if you don’t see it, you may need to update your account information.
To do that, click on "Account" on the left of your myOsmo home page and select 'At School' as the location where you use your Osmo.
To connect a device to your account with an activation code, open any Osmo app and tap the myOsmo button (or a profile avatar button) in the top right corner of the home screen. Then tap 'Log In' in the pop-up window, and tap 'School Login' to enter your activation code.