You'll get a course launch email by 9am US/Pacific time on the launch date.
You can log on to the Designlab platform at any point after you receive this email, so there's no worries if you won't be available that day or at that exact time.
Once you log on, you'll go through a short onboarding guide that will outline the course for you and describe how things work. You'll also be introduced to your mentor, and you can schedule your first Skype session with them based on their (and your) availability.
After that, you can dive into the coursework as your schedule permits!