To connect a device to your myOsmo account using your activation code, please open any Osmo app and tap the myOsmo button in the top right corner of the home screen. Then tap 'Log In', tap 'School Login' and enter your activation code.
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.
Also, please see our instructions for myOsmo account creation and management here: