How Do I Connect Bookshelf Speakers To My Mac To Use For Logic Pro X Output?

I have a pair of Polk Audio bookshelf speakers, I'm not sure what the model is. There are only two round ports on the back of each speaker, one of the ports has a negative symbol under it, the other positive. I am wondering how to connect these two speakers to my Mac so when I make beats in Logic Pro X, these speakers will be the output instead of my Mac's built in speakers.