I forced quit Mackeeper and turned off my Macbook. What should I do next?

I just know after install it that I shouldn't have downloaded it in the first place.

So, I tried to force quit and it's work! but when I tried to restart, it said Your computer can't be restarted now, because software is being installed so I held the Power button until my computer turned off.

When I turned on my computer again, I think there's nothing different but l'm worry that Mackeeper is still in my computer. What should I do next?