Where can I get api key for this plugin?

Please complete the following:

1. You must go to Google developers console and create a new project (set fields "Project name" and "Project ID" as you wish).
2. Go to the “API Library” and click the “Firebase Dynamic Links API” section.
3. Click the “Enable” button to activate the API library.
4. Open the “Credentials” tab and click the “Credentials in APIs&Services” link. The API key for browser application will be created.
5. Click the “Restrict key” button to prevent unauthorized use of the key in production.