This app comes with examples in /sdcard/Flashcard. Put your files there too. There are example files with 2, 3, and 4 fields of data. You can only have 2-4 fields. Fields are tab "\t" separated. You can use multiple tabs.
You can see that the data files have the category names (tab separated) on the first line. They have the category sizes in pixels on the next line. Then they have your data. You must have both of these lines at the top or the app will probably crash or gnash its teeth or something.
The files and the app handle utf-8. So plain English locale, ASCII and utf-8 will all work. If you don't use utf-8 and need it, do a web search for "Moodle utf-8". It is very helpful for Macs, Windows and Linux.
You can remove the examples if you leave the read.me file alone. Delete the read.me file to get the examples back.