I didnt have a clue either.
You have to download the "Zoom" app first and ensure you have a webcam on your laptop or a separate webcam which you can plug into your phone/tablet to enable the instructor to see and hear you.
Every morning,the instructor sent us an email with a link to click on which then took us to the "meeting room".
He did warn us of 2 points,
1. At any time,a member from DVSA could enter the room to ensure that everything was being conducted correctly.
2.We were warned that if we left the webcam for more than 5 minutes(say to use toilet,answer the door etc.) we would then be eliminated from that days course and have to re-book that days course.
We had the instructors phone number and in the event of a wi-fi or similar problem,text him immediately,and he could extend the time away from screen for 15 minutes maximum while we sorted the problem.