Garmin Edge: How to add lap markers to a course

[stratus5]

I have a recently purchased Edge 500 and am trying to understand the laps/courses thing ...

 

I completed an activity ... my daily commutes ... and have downloaded this as a course back to the Garmin. I did not put in any lap markers whilst doing the original activity.

 

When doing the course, I would now like to get splits for certain sections (a hill climb for example), so would like to add in some lap markers. Is there anyway I can do this manually (Garmin Connect etc), or do I have to redo the activity pushing the lap marker as required?

 

On that topic ... which is the best tool for analyzing your activities?

 

Thanks!