Task: I forgot to add a date and time to this reminder, so edit this reminder and set the time and date of the reminder to 6:00 p.m. on September 26.
Steps:
Click on the Good Bye, Lenin! to add date and time
Click on the Add date/time to add date and time in this reminder
Click on the Set time option to set the time of this reminder 
Click on the 6 to select the 6 in hours
Click on the OK button to set the time
Click on the Done button to save the reminder