If you’re on an Apple device, you need to select the document and it should open
automatically.
If you want to, you can save it by pressing Share (a square with an arrow pointing upwards located at
the bottom of your iPhone or the top of your iPad) If you scroll down.
After tapping the Share button, iOS will bring up a list of ways that you can share or save the file,
including sending it to others through text message or email.
Swipe through the list until you find the app you want to open it in.
If you'd like to save your documents to Files, swipe down the list until you see the Files option and tap
on it. Then, choose your save location.