How do you left click on a Mac?

Sorry for the newbie question, but I’m a newbie. I’m starting with Cubase 8 and I’m on Mac, OS X (I’ve been on Logic for years and am giving Cubase a whirl). I discovered the the right click equivalent is the Control key, but haven’t been able to find the left click equivalent, and it seems that left clicking is pretty basic and needed in Cubase.

thanks, and hi y’all!