To publish you iOS custom app on ABM you first need:
To have an ABM Account here is the guide to set it up
You need an Apple Developer Program Account
An iOS app ready to deploy
First login into you ABM Account, to to Settings, Organization Settings and choose Enrollment Information.
Here you need to copy your Organization ID, and enable Custom Apps if not already enabled.
Publish you iOS App
Please note you cannot change the distribution method (public or through ABM) once your app has been published.
Next, upload your app on App Store Connect (you can do that from Xcode directly).
Login to your App Store Connect console, select your app, and click on Pricing and Availability.
In the App Distribution Methods section select Private, and fill the form like this:
Type: Organization ID, in the ID field paste the ID you've copied from your ABM Account, and add the name of your Organization as displayed on ABM.
You can now submit your application for Apple review.
Once your app is approved you will have to either order redemption codes or licences to distribute your apps to your users.
You should now follow this guide to connect your ABM Account to Appaloosa.
If that's already done, you can distribute your apps using one of there two guides:
If you have our management options enabled please follow this guide for licences:
If you don't have our management options, please follow this guide for redemption codes: ABM without management