Use Firebase Auth information with Youtube API v3

Question

In my web-app I use firebase to sign-in users, what I get after a successful login is an object like that:

{
    uid: ...        
    ...
    stsTokenManager: {
        accessToken: ...
        apiKey: ...
        expirationTime: ...
        refreshToken: ...
    }
}

How can I use this informations to make authorization request to YouTube v3 API? Is it possible?

I've read the doc page and, as far as I understood, I've tried to send a request with this header:

{"Authorization" : "Bearer "MY_TOKEN""}

But I get this error:

Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup.