Ds help

Depending on the game, there should be a "Download play" option somewhere. When this is activated, the other DS must be in "Download play" mode also. This can be found on the main DS menu (hold start at startup). A small portion of the game can then be downloaded and played simultaneously or alternating depending on the game. Not every game is compatible with this feature.

If you mean literally play the _same_ game with both DS's... I'm not familiar with the specifics, but you'd have to take apart the DS, get the part that reads the cartridge, split all the connections and connect them to the same spots on the other DS... and chances are that wouldn't work either.