If you tap and hold on a data file attached to an email and don’t see an option to open the file in Graphical Analysis GW, it is probably due to one of the following issues:

1. You are using an app that doesn’t support “Open in…”, such as Gmail or Yahoo! Mail. Try using the option to open the file in Safari or set up and use the default Mail client on your iOS device. You may also try using the web version of the email client in Safari.

2. Graphical Analysis GW is not installed. Download the app from the App Store.

Related:
Can I open data files, such as Logger Pro or LabQuest files, in Graphical Analysis GW for iOS devices?
How do I import a data file in Graphical Analysis GW for iOS?