The Johannus One keyboard has a stereo line out for connecting the keyboard to an external sound system. You'll need a dual 1/4" cable available from Sweetwater
or Guitar Center
and other cable suppliers. These cables come in various lengths--9 feet or 12 feet will enable some flexibility in positioning the keyboard vs. the speaker system.
If connecting the keyboard to a house sound system via a mixer that is further than 12 feet from the keyboard, you'll need to use a stereo Direct Box
(or two one-channel Direct Boxes) and microphone cables to connect to the mixer or a microphone plug jack on the stage.