To install the Office.com/setup, follow the below mentioned steps:
For Windows PC
Visit office.com/setup and log in with your registered email ID and password
New users can select sign up and provide the required details for registration
Now, select Install Office and follow the further instructions
However, if you have purchased Microsoft Office that comes with a product key then enter the 25-digit key to the website to begin the download process.
For Mac
To download the Microsoft Office Setup for Mac, select the version from the list and simply click install to begin the installation.
Once the installation finishes, you will be prompted to activate the Office setup. Login to the Activate Office Wizard. For this, the prompt will ask your email id. Enter the id and choose "I want to activate the software over the Internet". Click Next to complete the activation process.