There must be a pick-up tube for adding anti-freeze for winterizing. Mix your bleach solution and siphon it in through that. That will sanitize your plumbing.
As for the tank, that can be a bit trickier..... If you don't have a "sanitize" feature for your tank, you can have someone hold the female coupling of a length or two of drinking water hose high, then fill the hose with your solution and a funnel. Holding it high allows air to escape. Once the hose is full, connect it to another hose that is connected to a water source, then force it into the tank with water pressure.
Be Safe, and Everyone Goes a Home,
2014 RAM Laramie 2500 w/6.7L Cummins Diesel and Automated Safety Hitch
2016 377RLBH Jayco North Point
300W of Suntech Solar w/Rogue MPPT Controller & Xantrex 2000W PSW Inverter