Run a search in Google or in the Play Store for Kingo Root. You download that to your PC even if it's a Windows system, then connect the phone via USB. Before you do that, you need to enable Developer Options by finding the Build Number in Settings, and tapping it seven times. Once you've done that, you can change the USB settings that Kingo will tell you to do.
All that said, the first thing to consider is what you hope to achieve by rooting.