NaOH, otherwise known as Sodium Hydroxide or Caustic Soda. I'd start with a small amount in water and see what happens. Add more crystals to water if it needs to be stronger. I don't think it takes much - the crytsalized packets of naoh that I use as developer are pretty small compared to the liter of water I put them into.
The manuf. states the water temperature should be room temp, so what, 20-22C?
When you're experimenting, remember to add crystals to water, not water to crystals.