On the People page from Admin, the "import people from csv feature" allows you, as the admin, to add or remove lots of people at once to your account.
Be sure to save/export your csv file as Unicode (UTF-8) which is usually the default for Excel or Google Sheets or Numbers, whichever one you work in. Two headers are required: Full Name and Email. If you want to remove a group of people then add the header remove_user and the type remove_user in that column. The video people should help to explain.