So that could be a number of things depending on the trackpad (personally, I prefer mouse and usually disable trackpad and pointer if possible)... if it's just one solid piece with the deck of the laptop, then it's usually double-tap. If it's a separate piece, then try clicking on the right-hand bottom corner (the Lenovos I usually work with usually have mouse buttons at the top of the trackpad, but they're the older models).

Worse comes to worse, take a photo of the trackpad and post it here.