There are many ways to learn how to test something:
- Training. Yes, this can work. Classroom or online, both count.
- Books. I still swear by "The Complete Guide to Software Testing" by Bill Hetzel. It's a bit outdated in some ways, but it's got a lot of things I can poke at and say, "oooh, is that relevant and how would I apply it?"
- Blogs and other online guides.
- Google. This one's great for learning specifics, like how to work with certain tools. I tend to hit this one late in the process.
- Past experiences. Things we tried that worked, or dev techniques, or things that failed. I learn a lot from coworkers, both testers and developers.
So keep in mind that learning counts, whether its formal training or something a lot more information. If you can to say, "what do I need to know?", then you can go learn it. Don't wait for the formal training. Just go learn.