Enable Gmail API and Calendar API on your project. You can use Google Calendar to notify users of an event or update their status. You can use Gmail API to send email messages. Perform the following steps to enable these APIs.

1. Click ENABLEAPISANDSERVICES on your dashboard.
   A new page named API Library appears. Next, proceed to Step 2.
   
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   Alternatively, you can follow these steps to visit the API Library page.
   1. Go to Navigation Menu on the Google Cloud Platform.
   2. Click API & Services and from the list of services select Library. An API library page appears.
2. Perform any of the following actions to select the required APIs. For example, select Google Workspace from the Category if you want to enable
   Google Calendar API and Gmail API.
   • On the left-hand side of the page, select a category and then select the desired Google APIs.
   • In the search box, you can search for the desired Google APIs
      

3. Select the following APIs from the library.
   • Google Calendar API
   •  Gmail API
4. For each API that you selected, click ENABLE.
   
   You can now access the selected API from your project.