Do I have to show up at a certain time?

No.

You can take the lessons whenever you like and at your own pace. And since the course includes lifetime access there's no time limit, so you can re-watch lessons whenever you need.

That being said, I recommend blocking out time in your calendar as soon as you've joined the course to ensure you complete the lessons at your desired pace. For example, you might schedule 2 hours a week over 4 weeks.