Below is the official guide:

For NDSi/NDSiXL/NDSiLL:
1, copy the correct _dstwo folder and ds2boot.dat file to the root of your microsd card.
2, insert DSTWO into your console. Boot the console, dont turn off it untill you see the DSTWO cart LOGO(the logo of Fish Tycoon, maybe need about 1 minute). Then re-boot your console.

For NDS/NDSL:
1, copy the correct _dstwo folder and ds2boot.dat file to the root of your microsd card.
2, insert DSTWO into your console. Boot the console, then re-boot when you entered the menu of NDS.

But this Guide for DSi and DSi XL, DSi LL is incorrect. You cann’t use DSi and DSi LL to install the kernel, the only one is use the DS Lite, So take care of to buy it if you only own DSi and the dstwo firmware not installed(Store: R4DS-DS have install the kernel for DSTWO).

1、Update the file system, remove checking storage space function to improve reading speed.
2、Added system file protection, user could not operate on system files to avoid system corrupt.
3、Fixed save problem, when the patch database save size is different from customer save size setting, will keep customer save size.
4、Fixed a cheat code bug. Sometimes, the cheat code does not display.
5、Fixed GameWatch Games Collection, RPG tools.
6、1222 – Archime DS (J)
2360 – LOL (U)
2645 – Bakushow
Fixed these game downplay function.
7、Added DSTWO provide Soft-Reset function for Homebrew. Any homebrew software run “_dstwo/reset2desktop.nds” file can return to DSTWO desktop.
8、Fixed ReadTime Save display time error bug.
Note: Old version patch database can not be use in new OS.

Download DSTWO V1.02 from r4r4i.com: Supercard DSTWO EOS V1.02

1. Fix “Made in Ore”&”RPG Tool DS”
2. Fix “4951 Daigasso! Band Brothers”,The save is normal now
3. Fix “4952 Prince of Persia(Black screen Error)”,If you want to play,Premise is clean mode
4. Increase capacity detect in disk for enter the game,Avoid roms generate the bad damage the game system Download&decompression DSTWO suite to root of TF,you’d better format the TF on first use
This suite contain DSTWO system core V1.01,GBA simulator V1.13,guide slot2 port&DS mode plugins and the latest moonshell software for DSTWO dedicated

Download: Supercard DSTWO EOS V1.01

Main feature list for SuperCard DSTWO:
1. RealTime Functions: RealTime Save(Enhanced, 3D game more stable), RealTime Game Guide(txt, bmp) & RealTime Cheat. (More stable, more easy to use, cheat code compatible with popular cheat file)

2. Multi Saves (Up to 4 slots), Easy to backup and restore saves.
3. New exclusive feature. Free Cheat function. During game play will allow you to search for and enable various cheats and hacks, such as modifying or even locking your characters health.
4. Unlimited MicroSD storage space support. SDHC support. FAT or FAT32.
5. Multiple languages (English, Simplified Chinese, Traditional Chinese, French, Italian, Korean, Japanese, Spanish)
6. Built-in GBA Emulator. More Emulator will be developed on schedule. Such as SNES.
7. Hotkey user-defined.
8. New Hardware Control Action Slow Motion (Up to 4 levels).

9. File Management System (Copy, Paste, Cut and Delete, long file name support).
10. eBook (BMP, JPEG, JPG, PNG, TIF, GIF, TXT, PDF).
11. New exclusive feature. Intelligent clean mode, automatically detect memory card speed and save type.
12. New exclusive feature. Hardware defence DS Anti Piracy. No Patch needed.

Download Supercard DSTWO V1.00 form r4r4i.com : DSTWO EOS V1.00

SC Team still have not released the DSTWO System files, we still need to waiting a little days. May be when most of stores have it, its will release the software files.

DSTWO Retailer:
1. R4R4I.com
2. R4DS-DS.co.uk

DSTWO System files: not available yet.