Learning to edit is the real trick. I learned mostly here in Share Your Work.

I'd stuff the novel away for a few months and go on a short story writing spree. Write a dozen short stories in a related area (if your book is fantasy, write fantasy, etc.). Short stories are easy to get critiques on. Critique everything that comes across the boards while you're doing this, and don't forget QLH. That place is like a whole course on story.

If you're like most writers, you'll need to see the mistakes in others' work before you can see it in your own. I learned as much from the critiques I gave as I did from those I received. Probably more.

Then, when you've grown as a writer and know some good, ruthless beta readers from your time in SYW, pull your work out and edit it again. Trade with your beta friends. Study story structure and use that knowledge to inform your revision.

I've used this cycle three times, and I'm just barely getting to where I think my work may stand the test of reader scrutiny. Your growth curve will vary from mine because we're different people. But it's a place to start. Hope this helps.