In a Google Workspace app (Docs, Sheets or Slides), click on Extensions > Add-ons > Get add-ons.
Type Phone Book in the search bar and press Enter.
Click on the Phone Book tile from the search results.
Click Install and follow the steps that appear on the screen.
You are going to be asked to grant permissions and to associate the add-on with a Google account.
 Click on Done to complete the installation.
Now you are ready to create a phone book.
You can also install the add-on directly from the Google Workspace Marketplace.