First of all, Go to office setup site.
Sign in with the account you associated with this version of Office.
You signed in with a Microsoft account.
Then enter your product key on specific area.
Before installation then enter product key.
From the Office home page select Install Office.
Select Install depending on your version then Install Office.
This completes the download of office setup to your device.
To complete the installation, follow the prompts in the "Install Office" section below.
Depending on your browser, select Run.
If you see the User Account Control prompt then select Yes.
Your install is finished when you see the phrase, "You're all set!.
To open an Office app, select the Start button lower-left corner of your screen
When the Office app opens, accept the license agreement.
Office is activated and ready to use.