Need to know engine and year of car before giving much advice, since the transmission could be one of several different models.

Basic process is to get transmission level, fluid heated to a specific temp (not fully hot or cold), run through the gears (manual selection is fine) then check level (how depends on transmission model).

You'll either need BMW software or a scanner tool to read trans fluid temp, or an infra-red thermometer.

There are two or three different transfer cases also. The later cars (LCI - version with X-Drive) transfer case require software to reset TC adaptations (oil wear) after fluid change.

__________________
Wayne
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)