goto Schedule -> Calendar in your Control Panel
click on empty time slot on calendar on Start Date of course
click 'Create Class'
Fill out applicable parameters.
After creating this, go back to the calendar and navigate to when you want this course to end. Click on the class after the last one.
A modal will pop up, click 'edit' in top right.
The last toggle is 'delete', set this to YES.
Select 'Delete this AND ALL future classes.' radio button below
Hit 'Edit Calendar item' to confirm.