You can update firmware using nRFgo Studio. This guidance covers some basic steps. More details about the firmware update procedure can be found in the firmware documentation.
If you are programming the DK add-on, the nRF52 DK has the SEGGER J-Link built in and can be used through the USB cable. If you are programming the product example, the nRF52 DK can be used as the debugger.
For links to the tools, see Nordic tools and downloads.