There is a bug in the iOS and iPadOS version of Graphical Analysis where the app won’t recognize CSV files as something that can be imported.
This is a bug and will be fixed in a later release.
In the meantime, a workaround is to install the older application GraphicalGW from Vernier, which can open CSV files.
Another workaround is to open the csv file in a spreadsheet, and using the clipboard to paste the values into Graphical Analysis.