1- visit https://console.developers.google.com/ and create your first project if it is the first time to use the API

 

 

2- at the “Library” tab search for “Custom Search”

 

3- Click the “Custom Search API”

 

4- You should find a “Create project” button if you don’t have a project, click it to create a project and if you already have a project, skip this step

 

5- Enable the API

 

6- Click the Credentials tab and click “Create credentials” then “API Key”

 

7- Once clicked, The API key will appear.

 

8-Just copy it to the plugin settings page then click “Done”

 

Important: please do not set any refer restrictions.