I struggled with this myself at first.
Suppose you created a new file, called listfruits.txt
The contents would look like this:
apple
orange
bannana
watermelon
If you import that to a list attribute, stencyl will create one entry for each. The first would be apple.
For a hypothetical map attribute, called 'cars', you'd create a file called mapcars.txt (you can actually name the file however you want). Suppose you have only one map key 'cars', with a few entries. You'd have a single line in the text file
that looks like this:
cars= Mazda, Corvette, Hyundai
And if you imported the file into a map attribute, the attribute would have one key with a list of three values associated with it. Hope this helps.