Welcome to iRV2.
The only RV , I ever winterized with an on-board tank for the RV anti-freeze, the two gal tank was beside the 12 volt pump, and the fresh tank, with a 2 way, valve inline to switch the pick-up line from the fresh tank to the 2 gal.
If you know where the 12 volt pump is and there is no tank beside it , your instructions may be for an older RV. The fresh tank, pump and 2 gal tank were under the bed, in the RV I worked on.
Putting RV A/F in the fresh tank is not rec-commended as the tank can pick up odor from the A/F that is hard to remove.
If there isn't a 2 gal tank you should buy a pick up tube; from an RV parts supply; that will install on the input of the pump and draw A/F directly out of the gal jugs the A/F comes in.