Go to Timecards > Timecard Tools: Assign Tracking Levels. You will get a screen like this:
Select the employee(s) whose entries you want to change, then select the entry type(s) you want to apply the changes to. Next, select the date range you want to include, then for each tracking level, choose "Employee default," or a specific tracking level item you want to assign to the entries.
Finally, select whether you want to include entries which have been modified by a user, and whether you want to change the pay rate to the employee's current pay rate, then press the big "Assign Tracking Levels" button.