Add enough water to cover ingredients, and mix well.
Set in refrigerator overnight (or for 4+ hours).
Enjoy!
Notes
A note about substitutions: You could substitute any kind of protein powder you like (for dairy-free/vegan versions), but you may need more water with other protein powders. Also, if you use quick-cooking steel cut oats, reduce the amount to ¼ cup (for this amount of liquid and these macros).