When you are given access to your Campus account, you log in using your email address and Campus password.
Once you are logged in to your account, you can decide instead, in the future, to sign in using your Google or Microsoft account.
To enable this, head to your Profile by clicking your name in the top-right corner of the page. Here, you will see the options to sign in with Google/Microsoft;
Select the relevant option, and choose which account you want to use. The button will then indicate that this sign in method has been configured;
Once you've set this up, when you want to sign in to Campus, select the relevant option on the homepage to sign in using your Google/Microsoft account.
Please note, if you have selected this login method, you will not be able to log in using your Campus password. If you want to switch back to using your email address and Campus password, just click the cross icon next to the configured method;