Login or register with a Google account and connect your YouTube channel.
Choose the languages you want captions on your videos.
You can try any plan for free for a week. No payment info needed. After that you can either signup for a paid plan, or use the free version.
Once you finished all steps, you just need to click a button to start. You can pause it any time.
*Once activated, every new video you post on YouTube will be automatically captioned with the languages you selected within 24 hours. You don't need to do anything, the subtitles will be already published on your YouTube video.