Youtube api problem please any professional guide?

hi, my browser app has just rejected due to API access to YouTube, i just figure it out your application cant be accepted if you put an youtube link , so for to enable youtube you need a API key , now i know how to get a API key but where to put it on thunkable. dont show me youtube extension cuz i know its to play YT videos just wants to know how to place a API key ! please anyone?

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