It's great that you're interested in learning SEO. To get started you could choose from the many SEO blogs to read (Moz, Search Engine Journal, Search Engine Watch etc.)
Don't just stop at reading. There are so many tutorials and other videos that can help you learn a lot. Gary Vaynerchuk's YouTube channel on SEO is one of the most influential. you can check it out along with many other great SEO channels available.
Finally you have to put everything you learnt into practice. You can start by opening your own website, preferably a blog where you can do as much as you can with your SEO knowledge. You can buy a domain name, server space and start your own blog through WordPress. Plus, it can actually earn you some cash!
Once you start your website, it doesn't mean that you have to stop learning. Continue being curious for more knowledge on SEO and continue being curious to experiment more on your website. That's how you learn SEO
Good luck. Hope this helped.