No 1 cylinder at the top of compression stroke. DC or TC on the flywheel centered in the timing window. Narrow side of the drive slot toward the outside of the engine and running straight with the block front to rear.
Slot will turn with gear teeth as it's installed so you will have to turn it a little past straight when you start so it will be even when you finish. Pretty much the same as installing a distributer in an old truck only the gear teeth are on the pump.