Transferring Nintendo DS games to an R4 card is easy if you are familiar with normal Windows applications and if your games are saved to your PC as ROM (read-only memory) files. The only difficulty is making sure you save the files in the right place so your R4 card will recognise the games when you use your DS or DSi.
Insert the R4's miniSD card into the card reader, then insert the reader into a USB port on your PC.
Open the miniSD card using Windows Explorer and navigate to the "GAMES" folder. If this folder does not exist, create it by right-clicking on the Windows Explorer screen, selecting "New Folder" and giving it the title "GAMES."
Copy the Nintendo DS ROMs to the "GAMES" folder on your miniSD card.
Return the miniSD card to the R4 card, and start your DS or DSi with the R4 card in the slot.
Choose "Play Game" from the R4 menu, and test the game to ensure that it installed correctly.
Although some R4 cards can locate games not in the "GAMES" folder, you will have the most success keeping them all filed correctly.
Downloading, installing or playing Nintendo DS ROMs for games that you do not own is illegal. Using or creating ROMs from your own purchased DS games, however, is fine.