Hello, and welcome to Drawspace.
The best advice I can give you is to practice with the lessons. Any artist needs to be able to see the values, shapes, and spaces to accurately shade subjects. The lessons begin with teaching you to see as an artist needs to. The lessons are accumulative, so start at the beginning to get the most out of them since they go by adding skills to ones previously learned. There is no fast quick fix technique - if there was we'd all be Masters

- , it's something you'll have to work on and build your skills. Just take your time, relax and have fun. If you practice and work at it, you'll get better. We'll be happy to help you any way we can. You can post in the Critique thread and you'll get plenty of good advice on the piece you post.