Perhaps the easiest entry point into fermented food is making sauerkraut. All you need is a jar that’s big enough to hold some shredded or grated cabbage. I added a couple of carrots to mine. Then just add salt and let the lacto-fermentation process begin. To avoid needing to burp the jar, I just covered it with some plastic wrap and a rubber band.
Press it down once a day to coax more liquid out of the cabbage and cover again. Keep it somewhere cool and dark. One week later, the perfect condiment for bratwurst or hot dogs. Or stew. Or just to have in a salad. Or try making some slaw. Or just eat it out of the jar.