There should be plenty of guides available how dosbox works. 3DS isn't much different.
Just mount a folder on your SD, and run a executable:
Code:
MOUNT C sdmc:/DOS/*somegame*
C:
SOMEGAME.EXE
Also check out the DOSBox wiki:
https://www.dosbox.com/wiki
The error message indicates no mapper file is found, it needs to be saved first to generate one. This message was mainly there during developing, and is subject to change to be less verbose.
The other is a button, try holding it for a sec. Again this is subject to change as my main focus has been on other functionality.
Otherwise, after trying out on multiple 3/2ds's, every time the 'dosbox-SVN.conf' file gets generated.
The only thing i can think of at this moment is to try and delete the '/3ds/dosbox' folder, and run the .3dsx from anywhere to have both the folder and configuration generate.
Did anyone else also encounter this by any chance? Every bit of feedback would be appreciated.