To activate your product key, please follow the steps below. 

Step 1: Please uninstall any previous versions of Office before installing this version. 

Step 2: Go to www.office.com/setup 

Step 3: Sign in with your Microsoft account, or create one if you don’t have one. 

Step 4: Enter your product key provided, without hyphens. 

Step 5: Follow the prompts to finish the installation process. 

For OFFICE 365, please follow instructions here
=> https://prowebsoftware.net/365-account-activation/