When you are invited to a private app, you receive the invitation by email. There you can accept the invitation to the app and thus start using it.
The sender address of the invitation is firstname.lastname@example.org. However, we place information about the actual sender - in our example "Contoso", in the information.
The email looks like this:
To accept the invitation, click the button in the email:
You will now be redirected to the browser where you can choose to forward the invitation to your smartphone or continue in the browser (web app).
If "Open as App" is not yet installed on your smartphone, you will be redirected to the App Store. There you can download "Open as App" for free. After installation, the process will continue automatically as soon as you start the "Open as App" app.
If it is a private app - which only people authorized by the app creator are allowed to use, you will get a (free) Open as App account during the invitation process, if you don't have one already. After registration (or login) you can now use the app: