Once your initial mix for the starter has begun to ferment, you'll need to feed it. Feeding gives the yeast more carbohydrates to digest allowing it to continue fermenting.
Uncover the starter and add:
100 grams distilled water or spring water
100 grams unbleached bread flour
Stir the water into the starter to dilute it, then smoothly stir in the flour. Scrape the starter into a clean bowl. Note the date and time of the feeding on the label, then cover the bowl. Here's my starter atop the refrigerator next to what's left of a 50-pound sack of bread flour and a gallon of distilled water:

Now, the waiting game again... If it's warm in the room, the starter should begin fermenting after 6 to 12 hours.