You can configure your AirPort wifi router via the AirPort Utility app. Apple AirPort routers have supported both the 2.4ghz and the 5ghz bands for several years, and both are enabled by default.
You can configure the router to use a different SSID for the 5ghz network. Using the AirPort utility, log into your router and go to Edit > Advanced > WiFi Settings and enter a unique name for the 5ghz network.