Importing Employee Website Login field

Content

I'm trying to change the current employee website logins from their current usernames "radams" to "exradams" and I'm unable to find the employee website login field. I go to Employees>Import>Import Employee data with a csv file but the login field isn't listed. I'm not sure how to get it added to that list as its available/shown on all the employee pages and it seems that all the other fields on the profiles are shown on that list. Am I in the wrong section? I'm also not wanting to create new employee records but just make a change in one field.