Reviewers may or may not attend the conference and may not have a profile in the system. Reviewers (and Area Chairs) get imported to their own table in the database.
From the Admin menu, choose Import → Reviewer and Area Chair Import. Step one allows you to import reviewers from a spreadsheet. Instructions are provided on the page.
Step 2, “Give complimentary registrations to classes of reviewers and area chairs, including creating missing local accounts” allows you to select a category of reviewer, e.g. Top Reviewers or Area Chairs and give then an immediate full, physical complimentary registration. If the reviewer doesn't have an account, one is created. If they've already registered, a refund is issued. This method of comping reviewers is consider legacy, because a comp is given regardless of whether the reviewer will use it or not.
A more efficient way is to invite reviewers to claim or decline their complimentary registration. For hybrid conferences, they can claim either a physical or virtual ticket. This method doesn't create a comp that won't be used and it doesn't inflate catering numbers.
Inviting reviewers to claim a comp is done mostly in the Django admin interface. However, the first step is the same as above. Once all your reviewers are imported, visit the “Reviewers” table in the Django admin interface. Filter for the current year, then filter for the kind and category of reviewer. Use the admin action “set_gets_complimentary_registration=True", then use the admin action “Invite to Accept, Transfer, Or Decline Comp”.
If you want a reviewer in the Reviewers table to be able to transfer their comp, use the admin action “Set Transferrable” before inviting them.