Video showing how to edit a csv file and mass import users into Salesforce Lightning using Data Loader
Link to salesforce sample:
https://help.salesforce.com/articleView?id=000327115&language=en_US&type=1&mode=1
Link to my sample data:
(Keep in mind that since I have used these usernames, salesforce will require you to use a new unique username. If you try to use mine you will get an error)
https://docs.google.com/spreadsheets/d/1B1x7uKACzIsi3TD2DRU8fyMpk5LhTn9yzloVE5IupTQ/edit?usp=sharing