Hello,

I have a 2014 Southwind and the owners manual says:  

1) To bypass the water heater, turn the lever valve vertical.

2) To supply water heater with water, turn lever horizontal.

It also shows a diagram, but I could not get it to copy here.

If you check on Fleetwood's site, you should be able to source an owners manual for your year.

Be sure to fully drain the water heater, leave valve open and pump in anti-freeze but no need to fill the tank.

I use about a 1/2 jug, close the bypass valve and continue winterizing the water system.

When finished, open the drain on the water heater just to see if any anti-freeze comes out.