Add .ics to my iphone calendar

Here's what happens...

1. in the email, it has a "confirm this appointment" button.
2. When I press it, it gives me the details of the appointment. it has a new button that says, "add to calendar".
3. When I press this button, it pops up a window asking where I want to add it - iPhone, Google, and outlook are the choices.
4. When I tap on the iPhone, I get a blank screen with three things at the bottom: a downward pointing arrow, the file name (appointment.ics - 350 bytes), "Download". There is an "X" at the far right.
5. So I click on "download" and it's still a blank screen with "Open in..." at the bottom
6. When I click on "Open in...", I get some options for airdrop, messages, mail, chrome, kindle, and other stuff - BUT NO CALENDAR OPTION. It says I can add a tag, open in downloads or save to files too.
7. If I open it in downloads, I see the file icon
8. If I click on the file icon, I see the entry in an image of a subset of a calendar screen with the appointment filled in, BUT THERE IS NO BUTTON TO ADD OR SAVE. THE ONLY OPTION IS TO CLICK ON DONE
9. WHEN I CLICK ON DONE, IT GOES BACK TO ICON PAGE AND DOES NOT ADD IT TO MY CALENDAR.

Can anyone help me, please?

there was nothing in my calendar inbox.