Do you have the stereo that was driving the motorhome speakers?
If you do then you will need an optical digital to analog converter. The optical output is fixed level so you will have to use the stereo remote to control the volume.
If you don't have the stereo you will need to get an AV receiver or an integrated amplifier with an optical input and remote control. You will have to remove the RCA plugs on the speaker wire and connect the bare + and - speaker wire to the AVR or amp.