Generally, the bypass system/valves (if actually installed) would be directly behind the water heater--should be a crossover line between cold in and hot out with cutoff valves on all 3 lines. If you cannot see this setup near the water heater, that is why bypass valve kits are sold. And, what type of AF did you get in the heater--auto or RV? If RV, no problem, it will rinse out; if auto, then more problematic as it is toxic to mammals, that includes us.
There is a Keystone Owners forum section if you scroll downward on the opening page--might find some help there. Keystone makes the Montana.
Welcome to the forum.