Make sure your new student joined Google classroom already.
If not - share classroom code with him and help him join.
Once he is in the class, show him how to find and upload homework.
Make sure the student has installed all necessary software. If he has any trouble with that - let administrators know (via Whatsapp or firstname.lastname@example.org).
Show the student how to bookmark Zoom URL for his future classes so he doesn't need to look for the class link each time (watch the video below).