Now you've typed The End, comes the fun stuff. At least for me. That's revision. What this means is looking at your finished manuscript with the eye of a reader or an editor. Parts of revision are easy and parts are hard. Spelling and grammar are helped by spell checkers but not completely. There are those words your fingers have typed but your head knows like not, rather than now. Those kind of mistakes. I remember in one of my books on the very first page missed by me, a first reader and the editor was toe rather than the. That's why not only do I look at the page on the screen but I print out every book and go over it, ruler in hand so I only see one line at a time.
There are other things to look at like the plot. Does it always make sense nomatter how fantastic the story. Are the characters true to their natures and if theychange is this reasonable and shown. Is the setting clear. Are the character's names consistent. Don't change the name in the middle of the book, or make sure you haven't mis-named a character bu slipping in a different name in one short paragraph.
You may find you need to re-write a scene. If it makes the story better, do it. Check the dialogue and make sure it's appropriate to the characters you've created.
When done, let it go into the wide world