Not only 4000 Watch Hours, to get approved for monetization on YouTube, you also need to complete 1000 Subscribers. Make sure your channel follows YouTube community guidelines as well.

After that, you need to have a Google Adsense Account to link it with your YouTube Channel.

What is a Google Adsense account? It's like a wallet to receive a salary from YouTube monthly.

If you don't have a Google Adsense account, you can register one then link it with your channel. It's just easy, like you create a Gmail account.

"How to create a Google Adsense account and link it with your channel?"

(Sorry because I can't write too long here)

Better you should Google it. You will find many tutorial videos that guide you step by step by the latest method 2021.

So, to answer the question, "How can I get paid after 4,000 watch hours on YouTube?"

The key is: Link your channel with a Google Adsense account.

Note: Make sure your channel meets all of YouTube's requirements for monetization. That's all.