Without starting the engine, unscrew the reservoir cap, wipe the dipstick with a clean rag and reinsert it into the reservoir.
The fluid level must be between the two marks on the dipstick Top up with ATF if necessary (consult a BMW workshop).
Start the engine and, if necessary, add oil so that its level is between the marks.
Stop the engine. It is allowed to raise the oil to a level 5 mm above the upper mark.
Close the tank lid tightly.