Using your Bb - un300 bottom bracket is easy. First, make sure your bike is compatible with the 68x115mm size. Install the bottom bracket carefully, following the included instructions and using the fixing bolts. When riding, you'll notice improved chainline stability, which makes your cycling smoother. As for maintenance, regularly clean the bottom bracket to remove dirt and debris. Check the bearing regularly to ensure it's in good condition. If you notice any unusual noise or difficulty in movement, it might be time to replace the bearing. Keep it dry and avoid exposing it to extreme weather conditions to extend its lifespan.