As stated above, you need an inverter- It "inverts" battery power (DC) to alternating current (AC). Get a "pure sine wave" inverter (they put out pure AC power like off the light poles), but they usually cost around twice as much as a "modified sine wave" inverter. Depending on how you wire it up it can power up some existing wall plugs to use for short periods of time. Some appliances, motors in particular, don't care for modified sine wave wave inverters- I learned that the hard way.
I just added one to my rig and I've been trying to complete the job for one and a half years-- I'm not too sharp on electrical systems. I also had to add an automatic transfer switch to prevent shore power from entering the inverter when setting up at a campground. Space and location is critical in the placement of the inverter. It has to be physically very close to the battery bank.
My initial aim was to just power up a small fridge/feezer, which I did with relative ease. I added the 1000 watt pure sine wave inverter inverter in a ventilated bay, on a shelf I added, close to my two house batteries and ran a 12/3 wire to the fridge/freezer compartment with a dual outlet plug. It worked fine. Then I decided to power some outlets for dry camping. That's when the work came in with the automatic transfer switch install-- ugh! all is well and done now. I think it is a poor decision for Motorhome mfg's to build motorhomes without one installed at the factory
Good luck on your inverter install. My 1000 watt pure sine wave inverter cost $450 just for the inverter. A dealer quoted me $2500 for them to do the job