Search your question on youtube as they have hundreds of DIY videos about anything and everything. You will need a good mask, probably a respirator to where while applying the varnish stripper. You should be able to get one at a big box store. And grab so heavy duty rubber gloves while you're at it to protect your hands along with some blue shop [paper] towels.

What about painting the four bar stools green to match my decor? So the kitchen chairs would a natural wood color and the 4 barstools around the island would be green? What do you think?

These photos might be helpful.....

And more....

I did not mean the stools with leather seats in the photo. I meant the ones that have the darker stain......

Well buy striper removal, scraper, protective gloves a mask and sand paper. start with 80 grid and down to 220 Grid buy 10 sheets of paper. put the striper on the chair wait intel it bubble up. than scrape all the stain off of it. Take you time. and then sand it intel the furniture is white. this process can take A couple of hours or days depending on the pice of furniture. I hope that helps

paint would be good.