Here is a snippet of code from one of my programs.
I have the files in a zip file so that the directory structure is maintained.
B4X:
Dim Writer As TextWriter
Dim Reader As TextReader
If Not (File.IsDirectory (File.DirInternal , "rounds")) Then
Dim MyZip As ABZipUnzip
File.Copy (File.DirAssets, "files.zip", File.DirInternalCache, "files.zip")
MyZip.ABUnzip ( File.DirInternalCache &"/files.zip", File.DirInternal)
End If
You can use the File commands to write to external storage, you can then write to these or read from them from within your app.
This requires the user to have say a memory card, although I think it is possible to also write to and from the apps location on your devices memory though that could potentially use up a lot of memory if the files were large.