The myGarmin site is for registering your device and to help you with maps and device updates and such.
Garmin Connect is the site that you upload your activities to so you can view them. For that you need to install Garmin Express if you want your activities to sync or upload to GC without a lot of effort on your part.
I am sufffering from the same problem, Since the updates I cannot find how to upload my workouts. Why can they not make it simpler to use. I do not need all the other guff.