YouTube blocks all users from streaming for the first time for a period of 24 hours to prevent spam.
If it’s your first time, follow these steps to request access:
You’ll then see a page like this, click the red Request button to enable streaming:
Once 24 hours have passed, you'll gain access to YouTube’s Live Streaming page.
There, you’ll find your Stream Key. Don’t change any settings, just copy the key to your clipboard.
Now go back to your YouTube account, your live game stream will be visible.
Click the Share icon to copy the live stream link and share it with your friends and followers.