For the latter option you need to have special hardware to transfer the .nds file to the Nintendo DS hardware.
I use the DS-Linker (16Gbit) for this task. DS-Linker is a flash/backup device that can be connected to the PC via USB, where Windows detects it as a regular mass storage device. You can copy files onto the flash-card with simple Drag & Drop operations. Once you have copied the file onto the flash-card, you have to restart the Nintendo DS and then you can start the program.
Official DS-Linker Website at http://www.dslinker.com
1.5.3