You can’t notify people the native app way (as in a pop-up notification on their phone).
The best you can do is showing new content at the top of, for example, the Home tab, so they don’t miss it.
This brings the question of how do you define “new” though?
Does “new” mean they haven’t read it? If so, have a user-specific boolean column called “Read”. When users open the item to read the details, before showing the details view to them, set the “Read” column to true. “New” in this case means “Read” is not true.
Or, “new” means it was added anytime between the past 7 days. Have a math column to subtract 7 from now, then filter by submission time (you must catch this when you add new items using the current date/time special value) is after the “7 days before” mark.