How do add brake fluid to a 2005 BMW 645 ci?

To add brake fluid to a 2005 BMW 645ci, first, locate the brake fluid reservoir, which is typically found near the back of the engine compartment on the driver's side. Remove the cap, ensuring the area is clean to prevent contaminants from entering the reservoir. Add the appropriate type of brake fluid (usually DOT 4 for BMW vehicles) until it reaches the "MAX" line on the reservoir. Finally, securely replace the cap and check for any signs of leaks or low fluid levels in the future.