Under your unit will be low point drains. Some units (RV's) have the valves hanging under the unit. Some valves are inside. Under the unit you can most times find by simple visual inspection lying on your back under the unit. There are three, one for cold water, one for hot water, then a third that is the fresh water tank.
Some RV's have the low point valves inside the unit. For fresh water tank drain, first find the tank. It will be directly inside, at the tank fill port you find on outside of unit. Pull whatever cover you need to pull (under dinette bench seat, or under bed, etc) and look around perimeter of tank. You will find a connection low on the tank with a valve. Pretty common to find t-handle poppet valves.
Since yours is a Class A, there very well may be all the valves mentioned located inside your water service area (compartment for for water/sewer service). Look along side of the compartment. Clear as a Frappuccino? Hope this helps a little.