So first things first, open the Google Home app on your phone and then tap the menu button. Next tap devices, then tap the menu button on the Google Home device the account is linked to. Then tap Settings and then tap link yiurvAccount. Next, tap continue, you can teach Google Home to recognize your voice by following the available onscreen prompts. Then finally tap continue.
Conversely, to remove a linked account, open Google Home on your phone. Then tap the menu on the Google Home that you are linking an account to. Then tap Devices, tap the menu and then tap Settings. Then tap Linked Accounts. Then tap the X next to the account you want to remove and then tap Unlink.