You've written a kids book. Congratulations.
Hopefully you are ready for the rules. to get this self-published.
1) Pick a printer.
Really it's first. Why? Because they all have their own little rules and idiosyncrasies that you need to follow for pain free publishing.
Almost all require 24 pages for publishing. (keep scrolling for the breakdown)
Go ahead and set up an account with your printer (if possible)and look around.
2) Pick a size.
This is important for several reasons. You want the size to be fairly standard, you don't want to be the oversized book that doesn't fit on my son's bookshelves (really annoys my specific brand of OCD), and you don't want to be the little book lost when another book pushes you out of the way.
There are standard options. Createspace (Amazon-KDP) has made it easy with a graph list. I made it even easier pick one of these six!
Little more advice here. The larger the book the younger the reader.
The bottom four I suggest for most first readers.
Top three for first readers and above.
https://www.createspace.com/Products/Book/ choose the printing options tab to see the full list.
If you've made this the first step, you're probably going to regret the choice. Take the book size you like. Make your illustrations the same size (or .375 larger) and DO NOT put anything important within at least .75 of the edge. All printers require bleed and margins. By keeping that space as background you won't run the risk of having an image recreated or cut off.
Make sure the files are big enough.
Please don't doodle on a post-it note and expect me to turn the cell phone image into something usable!
Printers require 300 dpi
I prefer 450 because when you change the size there is wiggle room to avoid DPI errors from printers even though you can bypass most DPI errors.
Margins and bleed are the number one reason that books get rejected by printers!
First page is the title page, a drawing with the author and illustrator listed(if the illustrator is listed as anything more than a thank you), or a repeat of the front cover (cover images are the same rules as interior, leave bleed and margins), or plain text with the same information.
Second page is the copyright. Yes, you have to have it doesn't matter how or where you are printing.
1) starts the story. This is a right hand page in the book. After that if you wish to have side by side pages that is fine.
2) is the dedication. Which means the fourth page starts the story and you can have side by side pages.
Two sizes. One full bleed, one not. Same starting order.
If you are having problems reaching 22 illustrated pages, the last one can be blank and the one before that can be an author page.
WHICH MEANS! You need a minimum of 19 pages of story and text to have a printed book(ebooks don't care)
Additional options: Text on one page, either with plain paper, colored background, image background (non-illustrated)
EDIT! EDIT! EDIT!
Once you've gotten this far, send everything to your favorite formatter. Like me!
If you send me a message and don't include the above information and the document the message looks about like this:
I'd be happy to help you with your book. Prices are based on the number of illustrations and text pages.
Who are you printing with and what size?
Please send me the full document(I prefer word, PDF will do) with some indication as to where the images go within the text, and illustrations (I prefer jpeg but almost anything will do, I can typically convert if necessary) and I'll make you a sample and get you a price.
I look forward to seeing what you have.
These are non-negotiable. LOL.
You would be amazed at how many people don't want to provide the information.
If you don't want to provide the information I really can't help you.
Once we establish the cost, based on the document I'll also need:
Author bio and picture if include on the inside or the cover.
Back cover "About the book".
Where do images go?
I've found a few too many people lately who make this very hard.
Really it's simple.
Each image has a name. Put in the text, (image name) goes here.
In a perfect world that would go something like Illustration one here. Illustration two here...but sometimes illustrations don't make it all the way to the end. New Illustration one here and new illustration two here, works well. Also little notes like--there is no illustration 18 (I will understand it's on the proverbal cutting room floor) even if that note isn't in the text, but an actual message/email to me.