When you’re creating new users, you can choose to do this in bulk.
The 3 columns you need are:
Column A: email address
Column B: first name
Column C: last name
Each row should correspond to one employee.
Additional columns you can use are:
Column D: role
Column E: team
You will want to add the managers as such and the same applies to admins. If you leave this cell empty the 'user' role will automatically be assigned.