You can use First Draft Pro on your iPad directly in the browser.
Go to app.firstdraftpro.com from Safari or your preferred browser
Log in with your Google account
Make sure your iPad is in landscape mode:
If you turn it to portrait mode, your app will tell you that First Draft Pro does not work on mobile devices. This is because First Draft Pro only works on screens of a certain size, and when your iPad is in portrait mode, it is no longer the correct size.
Collapse the right-hand side menu to create more space for writing:
Expand the menu to see your notes and comments:
Tap to create scenes: