Greetings BaNoi,
You can learn how to sign in to FaceTime on your Mac by following the guidance found here:
Sign in to or out of FaceTime on Mac - Apple Support
"Sign in and set up FaceTime
You need to sign in to FaceTime the first time you open the app, or if you’ve signed out.
- In the FaceTime app
on your Mac, enter your Apple ID and password. - Click Next. FaceTime is on automatically.
- If you forgot your Apple ID or password or if you need to create an Apple ID, go to the Apple ID account website.
- Choose FaceTime > Settings, click General, then do any of the following:
- Choose how people can call you: Below “You can be reached for FaceTime at,” select the checkbox next to each address and phone number that you want to make available for FaceTime calls.
- See the conversation as text: Select Live Captions (Beta).
- Note: Live Captions is currently in beta and is only available on Mac computers with Apple silicon. Live Captions is not available in all languages, countries, or regions. The accuracy of Live Captions may vary and should not be relied upon in high-risk or emergency situations.
- Take Live Photos in FaceTime calls: Select “Allow Live Photos to be captured during Video calls.”
- Choose the phone number or email address other callers see: Click the “Start new calls from” pop-up menu, then choose the phone number or email.
- This only appears if you have more than one email address or phone number set up.
- Change ringtones: Click the Ringtone pop-up menu, then choose a new ringtone. See Change FaceTime ringtones.
- Change location: Click the Location pop-up menu, then choose the country or region that your FaceTime account is registered in.
- Choose the default app to start calls from: Click the “Default for calls” pop-up menu, then choose an app.
- This option only appears if you have more than one calling app on your Mac.
- Choose FaceTime > Settings, click SharePlay, then select SharePlay.
- You can view TV shows and movies together, listen to music together, or share your screen during calls."
Take care.