Measure 4 ounces by weight of whole wheat or whole rye flour (a scant 1 cup by volume) and 4 ounces by weight (1/2 cup by volume) of lukewarm water into a food safe container. Stir until no dry pockets remain. It'll look like this.
Cover this loosely. This could mean you lay a lid that fits the container on top without snapping it into place OR that you lay a piece of plastic wrap or waxed paper over the top.
You're looking to make sure some air can get in and out while trying to minimize evaporation and keep it moist. A tight fitting lid can literally blow off of an active starter, so loose fitting is always going to be the name of the cover game.
And while we're talking about the name of the game, consider the temperature of your room. If your room is below 68°F, like my cool-climate house, you'll want to find a place that IS at that temp or above to help coax your starter into reliable activity.
If you just plain don't have a part of your house suitable to do that, you can pop it -still loosely covered!- into a cold oven with the oven light on. The light should provide enough heat to keep your stove the right temperature to encourage starter growth.
If your oven light is out, you can lay a folded towel over a heating pad set to low and put your container of starter on top of that. Some other good, warm-ish places are behind a woodstove (ask me how I know), on top of a refrigerator or desktop computer CPU, or next to (not directly in front of) a space heater.
The goal is just to find a place that has a steady, warmish temperature to grow your starter but not a place that is wickedly hot or drafty.
SAMPLE SCHEDULE TIME: START THE PROCESS AT 9AM.