Ask the local music association if there is such an association in your area. If so, write an application and they will send you a membership form. You fill it out and once it is approved, you will be a member. Generally speaking, membership requires certain qualifications, works, and performance awards, etc. The requirements and restrictions are probably not too high in your case. The provincial Musicians Association requires a deputy senior professional title, while the Chinese Musicians Association requires a full senior professional title.