Training: With Butt Plugs

Honey
Okay so I went and bought butt plugs for beginners. It has small, medium and a large plug. I just have a few questions. How long should I leave the small one in for while wearing it? When should I upgrade to the next size? Do these really work to help train your butt for anal sex? If you could please help me out that would be awesome! Thank you!!:)