Below is a description using the example of AT A5S 310Z.
1. Remove the ATF drain plug (1) and drain the ATF.
2. Remove the bolts and oil pan.
3. Clean the oil pan and magnetic disk.
4. Insert magnetic disks (1 and 2) into the oil pan. Check the sealing gasket (3) and replace it if necessary.
5. Install rounded brackets in the corners of the oil pan.
6. After finishing the work, fill with ATF (see chapter Vehicle settings and routine maintenance).
The original source of the article is on the website «BMWman»