If you have been supplied or purchased Office 365 have a product key, you will now need to link the code to a Microsoft account to install Office 365.
To setup Office 365 with a product key:
Go to Office.com/setup
Sign in to the Microsoft Account you use for Office 365 (If you do not have an account, create a new account and you can use your own email to do this)
Enter your 25-character product key and choose Next
Choose your Country or Region
Choose your Language and then choose Next
Automatic Renewal is on by default, choose Next and enter your payment details
NOTE: If you leave on Automatic Renewal, you will be required to enter your credit card details. If you do enable automatic renewal, you can turn it off at anytime.
Choose Next and then Next one last time to complete the renewal
For further information, you can also go to the following website link: Microsoft renew with a product key link
If you have any issue renewing via your Microsoft Account page, try using this alternative redeem method instead.