On your device, head straight to a web browser.
Tap on the Address Bar.
Then, go to the MS office Official website.
Now, Enter product key on your system.
On the MS Office web page, search for the Sign-in option.
Click on the best match.
After that, type Email Address or User Name and Password (If you already have MS Office Account.)
If you are a new user, then click on Create MS Office Account option at Office.com/setup.
Then, select the MS account version, i.e., either work and school, or Microsoft.
Next, pursue the prompts and continue further.
Once finished, a window will pop up.
Then, tap on the Continue icon and begin the downloading procedure.
Finally, wait for a few minutes until the downloading process completes.