The main qualification required is the determination to become a tester and some patience along with a mindset of giving up even if you fail million times.  When you are ready, enrol for a course in class or online and start doing beginner level testing sample projects to be job-ready. You may read some books as well regarding testing or excel in one or two software testing tools. When you are confident enough, you can apply directly to companies or start with freelance work to gain some experience at the beginning.