There is detailed DSTWO setup guide from supercard.sc, and users can refer to its official page http://eng.supercard.sc/manual/dstwo/download.htm.

Note: You need to install its latest EOS if firmware update required, or it will not work.

Firmware Upgrade

If your 3DS XL system blocks your DS2, gets “An error has occurred” when you try to boot DS2, or will simply not start for whatever reason (doesn’t show up on 3ds menu/white screen, etc), or has a Fish Tycoon logo, you can follow guide below and try to fix the problem.

Problem fixing for DS2 owners – Thread from DSTWO Official Forum.