There are many different paths to becoming a composer. Some do a lot of formal study. Some try to do it all on their own. Some people like to work with others, like in a band setting, and others prefer to work alone. You have to find your own muse and follow it to wherever it may lead.
Some people need to figure it all out and master other people's compositions before they start their own writing. Whereas some people, like Joni Mitchell for example, admitted that she didn't have the technique to play other people's music so she just went out and invented her own from scratch.
Like I said, there are many different paths, you have to figure out what works for you (and that usually involves a lot of experimentation).