right ok this may not be exactly right as I have never bred them myself,
from what I read you are best to get up a 10-15gallon tank, with two or three females and a male.
You need to stack marbles in the bottom of the tank, about 3-4 marbles deep.
Danios are egg scatters and they eat their own eggs, so the when they spawn the eggs will fall between the marbles.
Once that have spawn remove the adults and place them back in their main tank. Now slowly and carefully remove the marbles. making sure you leave all the eggs in the water.
Then once the fry are free swimming you can feed them newly hatch bryne shrimp and powdered flake food for egg layers.
ask in the charachin forums for better details, I'm sure someone there has bred them.
As I said I have never bred them myself, and I read how to breed them maybe 8months ago or more so some details may have been lost in translation so to speak.