installing back-flush kit on 1995 Olds

I'm installing a prestone back-flush kit and can't tell which is the heater
hose that runs from the heater to the waterpump and which is the heater hose
that runs to the top of the engine. I think I guessed wrong because when I
run water into the fitting it is not moving thru to exit at the radiator. I
installed it in the higher hose that didn't have a mesh shield on it
(figured higher is higher to the top of the engine.) This is a 1995
Oldsmobile an 88 model with a 3.8 cu in engine. I don't have a chilton's
book to see which is which. Any help? Mark