If you mean by Wi-Fi, you need to have it and go to the DSi Shop Channel.
Chat with our AI personalities
You can download unlimited, full version Nintendo DS and DSi games and easily transfer them to your DS / DSi using: http://www.squidoo.com/Download-DS-Games
You can't download games onto a DS Lite.
No. There is no way to download or play DSiWare games on Nintendo DS or DS Lite systems.
On the newest DS systems, you can access the Nintendo eShop, which allows you to buy and download games if you have an internet connection.
You can download games from other people with a person who has a ds and also from your wii.