Typically, the bypass valves are directly behind the water heater. You may have to remove a fake panel, door, or other things to gain access. In my travel trailer, I have to remove the bolts to a fake hinge and remove a cabinet door to gain access.
The easiest way to see, is to know where the water heater is located, as I pointed out in a pic from outside your RV below, then go inside and see how to get to the back of the water heater.
Some RV's actually have the bypass valves inside the plumbing hatch. Also see pic below.