Feed once a week.

Measure the current weight of your starter. Note the weight of the container on the side. (Many people use painter’s tape and a sharpie.)

Mix an equal weight of warm water and an equal weight of flour into it. (ratio 1:1:1)

Let it sit on the counter at room temperature with the lid opened so that it can develop.

If you need to store for longer, you can close the jar and put it in the fridge.