Don’t store ground coffee? Buy an inexpensive hand grinder from someone who’s moved up to a more expensive model and keep your beans whole until you’re ready to brew.
Coffee stales amazingly quickly and there’s really no good way to prevent it, the longest I’d store ground coffee for is like half a day (if I’m taking some ground coffee to work to make a cup mid day.)
If you absolutely must store ground coffee an airtight container should work but it won’t be terribly fresh after a day or two.
guyrocket