How do I delete the League of Legends download from my Macbook Air?

My boyfriend downloaded the game on my Mac off the internet, and since I never use it when I'm not with him (not to mention I'm wary of the potential risks of random internet downloads for 1,000 dollar computers) I figured I'd delete it. HOWEVER, it won't let me! Whenever I go to my Launchpad and press on it to evoke a delete button, or try to drag it to my Trashcan, it won't budge. It's as if it's as imbedded as Safari or other predownloaded apps. I'm an inexpirienced teenage girl who only knows computer basics. Help!