iCal Problems?

I recently downloaded OS X Mavericks on my MacBook Pro and it comes with a new look for iCal. Everytime I try to create a new caleneder group it makes it, but when I go to choose it for an event I can't click on it. This has never happened before when I was using the old version of iCal. Being a busy student, I use iCal alot for after-school activites, appointments, tests, quizes, etc. Is anyone else having this problem or know if I'm doing something wrong?