How to get Search API key
To get your API key, you need to go to Custom Search Introduction section and click Get key.
The popup window will come up. Here you need to Enter new project name, tick Yes box to accept Terms of Service and click Next.
A new popup window will appear where you can copy Your API key to paste it to the widget.
If you need more, you may sign up for billing in the API Console. Additional requests cost $5 per 1000 queries, up to 10k queries per day.