i take it to mean you want to wire the 3 - 4ohm subs as a 1 ohm load.
if you wire them all in parallel, the load comes to 1 and 1/3 ohm.
take 1 set of output wires from the amp, on the "plus" wire, wire nut on 3 more wires which will go to each of the 3 subs "plus" inputs.
from all 3 of the subs "minus" inputs, wire nut those 3 wires to the "minus" output wire from the amp.
remember, resistances in parallel divide, resistances in series add.