If you put the oil into the engine via the oil fill on the rocker arm cover and the oil is not showing on the dipstick I would guess it went into the piston chamber(s). Please determine where the oil went prior to trying to start the engine. You can rotate the engine manually by placing a socket on the front crankshaft bolt and determine if the engine will turn over freely. If oil is in the chamber the engine will only rotate so far and then lock. If the oil is indeed in the piston chamber(s) and an attempt to start the engine with the starter is made, serious damage could occur. If the oil is in the piston chamber you will need to remove the glow plugs and manually rotate the engine to blow the oil out.