I’d encourage you to try the app(s) out so that you can see what new users see. It’ll help with guiding them toward fixing issues that they may run into (like how to edit an observation from mobile to remove the extra photos).
I can only speak to Android, but the “on-boarding” / tutorial / getting started guide is not very extensive. It says your observations should be your encounters, but doesn’t specify that you must use your own photos. Nor does it really discuss other “best practices” like being sure to mark as captive/cultivated. Nor does it say to go to the iNaturalist.org website, just “check back [here, in the app]”. I attached some screenshots below.
Opening iNat Android App and creating an observation
As of 29 August 2020
Tapped View Nearby Observations
Tapped Allow
Opened hamburger menu (top left)
Tapped Log In / Sign Up and chose Create an Account option
Logged into account and created an observation
Saved observation and it synced
As far as the topic title, there’s some good information in the Community Guidelines and several prepared responses for common issues that pop up on iNat.
Oh, and if you joined iNat forever ago, here is what the welcome email looks like that new users receive. So there is some direction as far as how to use iNat with some links to visit the website, if they read the email that is ;)