You maye either test images with emulation or install images on the DreamPlug hardware.
use the image with VirtualBox
You can use VirtualBox to run the image in a virtual machine. These instructions have more details:
use the image with a DreamPlug
You can install the image to your DreamPlug directly.
See FreedomBox/DreamPlug/Images for available downloadable images.
If you've bought your own DreamPlug, you will probably need to flash the firmware, which requires a JTAG. Follow these instructions: