You can use the K12 as a stand-alone PA system, without the need for an external mixer. Simply attach a microphone directly into its XLR combo input, and if needed, attach a second sound source to the other XLR combo input, and a third source (such as an MP3 player) to the RCA stereo input.
There are two gain knobs that you can use to balance the mix, and a dedicated XLR output that outputs the mixed signal to a second K12 or any other active loudspeaker. For more involved professional installations, there are designated suspension points and kits available, and a Euroblock connector to remotely control the gain.