Hello, forgive me if my question seems stupid, I’m just not a programmer 
I generated an API key, now how can I get the CX parameter?
EDIT:
I guess I was a little hasty with the question, although finding the instructions I needed took a lot of time. But still I found instructions in Russian. Maybe someone will find this useful:
Create your own custom search system
To get the CX parameter:
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Click “Get Started” and sign in to your Google account.
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Click New Search Engine and follow the instructions to set up a custom search engine.
- Enter search sites (eg https://www.nytimes.com/ or https://www.bbc.com/').
*Name your search engine. - Click “Create”.
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Customize your search engine by adjusting the settings in the General and Sites to Search tabs.
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After saving the data, the Search engine created notification will appear. Go to the “Settings” tab to get the “cx” parameter, which will appear next to the
Search Engine ID.