There are a lot of different avenues to becoming an editor, but one of the simplest things you can do to prepare you is to read a ton and don't forget to write. Read a variety of things, and pay attention to what works but also to what you would change to make the book better. Practice writing about books, writing up a blurb for the books you love, writing reviews of the books you read: even as an editor, you'll be writing all the time.
Another great way to gain some preliminary experience is to offer to provide critiques or to beta read writers work. There is a beta readers group on Goodreads -- https://www.goodreads.com/group/show/50920-beta-reader-group , and one of my favorite places to exchange critiques is the KidLit 411 Manuscript Swap group on Facebook -- https://www.facebook.com/groups/KIDLIT411MSswap/. Their website also has a ton of great resources if you are interested in kids lit.
If you want to work with one of the large publishers, studying writing, English, communications, journalism, or publishing in university is a good way to get a foot in the door and open up opportunities to apply for internships.
Best of luck and happy reading!
Then try to get some experience by looking to volunteer to do editing. Hopefully you can with folks that can give you leads on some paying jobs to get more practice. From there you can start your own editing service or applying for jobs.
I agree with Brittany. Developing your own writing skills is essential to becoming an editor. You need to be able to communicate clearly, succinctly, and accurately both in writing and in person. Constantly revise and edit your own writing. Your knowledge of grammar should be flawless.
Location matters less today because so much editorial work happens online. To build your own online professional community, use LinkedIn to network. Take extra care creating your profile because it serves as today's virtual resume. Connect with book editors who work in the genres that interest you and comment thoughtfully on their relevant posts and share them. Keep in mind that every time you write something online, it's a writing sample to an editor reading it. Likewise, post and comment on links to industry-relevant content, and tag editors you think might be interested.
However, don't focus on your number of followers or let online networking take up too much time! Stay focused on developing your core skills: reading and writing.
Elizabeth recommends the following next steps: