Take the classes and then you can either do clinical/student teaching (don't get paid but certified after 10 weeks) or internship (get hired, get paid, but not certified for a full school year). Then pass your TExES exams and you're certified.
The classes can take from 2 1/2 to 6 months depending on the program and format.
My degree is in jazz performance. I started alternative certification in the summer. It was online and took 24 weeks. I did clinical teaching in the Spring and was fully certified by May.