Custom App Distrubition

My company has a developer account and also has a company id. We want to publish our app through the Custom App, but we have failed. The software company writes the application and the software company has an enterprise developer account. The software company cannot access the itunes store. we couldn't find a document explaining exactly what we should do. We looked at Apple's websites and blogs, but the documents we read were very poor. My question is that: how can we publish our application through the custom app?
Custom apps are published through the regular Apple Developer Program, not the Apple Developer Enterprise Program. If you do not have an Apple Developer Program account, you can sign up for one here:

https://developer.apple.com/programs/enroll/

Once you sign up, you can then publish your app as a custom app by selecting to make it available privately.
Hello Developer tools Engineer,
you said that "Once you sign up, you can then publish your app as a custom app by selecting to make it available privately."
then what we will do ? We chose the application as a special application on the apple store. The application was also reviewed. How will our customers download the application? As far as I researched, users do not see the application on the apple store because it is private.What are the steps of these processes.?
@developerms your customers will use Apple Business Manager to download your app. I wrote an article with more details at getonthestore.com/private-app-distribution.
Custom App Distrubition
 
 
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