Add Programmable Search Engine to your site – Google Help

Once you’ve created your Programmable Search Engine, you can add the Programmable Search Element code to your site. To do this, you’ll need to copy some code and paste it into your site’s HTML where you want your search engine to appear. From the list of search engines, select the search engine you want to implement on your site.

https://support.google.com/programmable-search/answer/12423533?hl=en