How can i connect my Nintendo DS to my internet ?

You can't. When DS or Wii games go online, they connected to a service called Nintendo WFC. This service was taken down in 2014, so you can't go online with DS or Wii games anymore.

It's not possible anymore because they shut off Wifi services for the DS a few years ago.

https://frontier.com/helpcenter/categories/internet/installation-setup/connect-my-gaming-system/get-started/console-instructions#/collapse1

ggg

Use your penis