How to start learning guitar and become a master at it?
In general, when learning a hands-on skill such as playing a musical instrument, there is no substitute for hands-on time and deliberate practice. Often, people learn best when they are pursuing specific goals. For guitar, this might mean working toward being able to play a particular song you already like. Practicing regularly, ideally every day, will help you build muscle memory for your instrument. There are many resources available to ensure you have the right technique and to learn the basics of how to make the notes on your instrument; you can purchase books at a store, find them online for free, or use Youtube videos for education. If you are not as good at self-directed learning, I would recommend finding a teacher if you have the resources to be able to. 

If you have never played a musical instrument or sung before, you will also likely have to learn basic music notation and theory (the basics of rhythm, pitch, etc.). 

Becoming a master is not easy and you will need to work very hard for a long time. However, the learning process can be fun and even if you don't become a master, it will be a very rewarding and enjoyable experience.