Put the peppers in a clean jar and cover with water. Poor the water out into a measuring cup. Replace half of the water with vinegar, to give 50-50 water and vinegar. I used a mixture of sherry vinegar and white vinegar, but any vinegar will do as long as as it is 5%. Heat on the stove to dissolve 2/3 tablespoon kosher salt into vinegar mixture and pour over peppers. I added some whole coriander, but you could use cumin, garlic, pepper corns or other herbs. Cover and refrigerate. It will take a couple of weeks for the flavour to mature. The peppers should keep indefinitely in the fridge.
If you have more than a couple of jars and don't want to store them in the fridge you'll need to sanitize the jars and lids, and process the packed jars in boiling water. Check out www.instructables.com/id/Pickle-Anything-Basic-Pickle-Instructions/
for more info.