There's going to be a lot of possibilities here... but for a simple example, you could just do a check if a Pad direction is held, then move the sprite by incrementing a variable that represents it's x or y position and move the sprite to the new position.

There's some stuff on this in the tutorials for sure. Without any of the other setup of loading the sprite into memory or anything, this would move a sprite Right 1 pixel every VBlank, or 60 pixels per second. I'm sure you could figure out the other directions.

x = 50
y = 96

while 1 == 1 do

if Pads.Right() then
x = x + 1
sprite.MoveTo(x,y)
end

DSLuaWaitForVBlank()

end