How can I install the app for iPhone to iOS Simulator on the ARM/M1 powered Macs?
You can go to the App Store on an M1 mac.
At the bottom left where you see your name, click on it.
Your account page will appear.
Under the word 'Account' are two buttons, 'Mac Apps', 'iPhone and iPad Apps'
Click on 'iPhone and iPad Apps'
Now you will see a list of apps on your iPhone and some that are not but perhaps you once had.
Click on the 'open' button on the app you want to run and the app will start.
Note this is not the simulator but the REAL app. To debug this app you need a debugger.
Use XCode's debugger
https://developer.apple.com/support/debugging/
Here is an introduction to the debugger
https://raygun.com/blog/debug-ios/
Here is a more complete reference
https://www.tutorialspoint.com/ios/ios_application_debugging.htm