You don't. Neutralization reactions occur between an acid, such as the acetic acid in vinegar, and a base, such as baking soda. BUT, and it's a big BUT, they generate HEAT when they do. And it can be enough heat to burn your skin. So as a general rule DON'T DO CHEMICAL REACTIONS ON YOUR SKIN.
Instead, flush the area with the vinegar with lots of cool running water, and that will mechanically push the acidic acid molecules of the skin into the water stream, and it will also dilute any acid remaining on the skin, and will not be heated by being diluted so to won't get burned.
I have had the unforgettably horrible experience of having a medical treatment where a syringe broke spilling a weakly acidic substance onto a tender area of the body where it got on a mucus membrane, and the doctor looked up online what should be done besides flushing with water, and the advice was to have a sitz bath with baking soda, and I can testify YOU DON'T WANT TO DO A NEITRALIZATION REACTION ON YOUR BODY.!!!! It was bad. I ended up with that area of my body covered in second and third degree burns. The heat of the neutralization reaction did that, not the original acidic substance. It wasn't capable of that intense of a reaction with just skin, but it reacted vigorously with the baking soda and it's not something you want to find out how awful that is. Trust me on that.
