To edit users:
you either must have the system role "admin" assigned
or you should have the "Manage users and roles" user role permission
Perform the following:
In the bottom of the navigation pane, click Settings.
Click the Users tab.
Click a team member. The user profile appears.
In the upper-right corner, expand the menu. Click Edit.
Here you can edit the first and last names of the user.
Click Save user.
Navigate back to the Users page.
How to edit the names of a user through Settings > users
How to edit the names of a user through People > employees
How to edit your name in My Profile