Before becoming a K-pop star, aspiring idols devote themselves as trainees for how many years before debuting as an artist. Most spend their youth practicing and perfecting their singing and dancing skills in hopes of becoming a certified Korean pop star soon. Thankfully, there are ways on how to be a K-pop star.
KPOP S.M. Entertainment always holds a global audition for KPOP. There is one online (Amber from F(x) became a trainee through this process), and S.M. holds physical auditions in different countries, though locations can be limited. The auditions are usually held in big and major cities (for example, Los Angeles in the US), so if you don't live near one it could be a hassle. Unfortunately, if you live in the U.S., the S.M. website says that the auditions there have been canceled for a few months.
The website I linked below has more information. For the online audition, I believe you send a video of you singing, dancing, etc. If S.M. is interested, they will email you back. I personally don't know much about the online audition so I have linked a helpful Wattpad post that goes in more detail about it. I urge you to read it if you are serious about auditioning. But some background information you should know to understand the Wattpad post is that 'everything' is a karaoke singing app you can actually audition to SM Town with. You can download it on your phone and practice your singing.
SM is always holding auditions, in fact, they do almost every year. But more companies like JYP, YG are always recruiting new and fresh talent but if I were you I would audition for a company that will treat you well like JYP they always put their artists and staff first before anyone else and they are very loyal when it comes to artist management and don't audition for companies like YG they are the exact opposite of JYP they don't do well enough to take care of their artists.
Even BigHit does global auditions. But most entertainment companies scout their artists from all over the place. Even around the world. If you look online there are many idols who talk about how they were discovered by their new company. It is best to get trained before applying as a KPOP Star.