Welcome to the forum
On automatics you MUST install the torque converter on to the transmission input shaft first, you need to spin it and it will slide back into the bellhousing and it will line up the PUMP and INPUT SHAFT splines
You will ruin the transmission if you do not do this, period
As you turn the torque converter it will slide back 2 or 3 times as slots and splines line up INSIDE the transmission
You need to remove all Spark Plugs first, then you can install transmission to engine block, don't forget Block Plate, its a thin metal plate used as spacer and to align starter motor to flexplate
Once you have 2 to 4 bolts in place, but loose, for bell housing to block then you can use a socket wrench on the Crank bolt to turn the engine to align torque converter to flexplate and bolt it in place
THEN you can tighten bell housing to engine, and it should just push on, flush, if you have to force it on to the engine something is WRONG