Once you've scheduled a private session with an instructor, you'll receive a confirmation email with the date, time, and info about the instructor you'll be working with. In this confirmation email, you'll find a link to a Zoom meeting. At the time you're supposed to meet your instructor (the time listed in the confirmation email, the one you chose when scheduling your session), just click that Zoom link.
If you've used Zoom before, it will open and your session will begin! If you've never used Zoom before, it will download automatically and you'll need to enter your email and a display name to continue.