Welcome to the rudest, most deliberately unhelpful forum on the net - GBATemp.
It is generally not a good idea to ask for help here.
Ignorant children who do not know the answer will try to make you feel stupid because you do not know either.
Even if they do know they would rather make fun of you than try to help.
Try "root" for the username, then "uClinux" for the password.
You may also need a slot-2 device.
DSLinix Wiki
QUOTE said:
Whilst popular, Slot-1 cannot provide extra RAM that DSLinux needs for lots of its features. Therefore, a Slot-2 RAM extension such as the one supplied with the Opera DS browser is recommended if you want to run DSLinux with a Slot-1 device.