Modifying Users in Ad

Modifying Users in Ad

How do i bulk Modify my Users

Problem When AD setup the First Name has been setup with the Users username
IE

Firstname spurvis when it should have been Stuart
Surname is Blank

User login is spurvis

I can export all the users to excel with Admanager but it is not in the same format for importing in when you try import modify users csv

Can some please give me an example of the correct format i need to have to modify import csv for excisting users

Thanks
Stuart