Department stores have multiple make-up counters for different cosmetic companies, all of whom will let you try on a product for free. They can apply it for you - you might ask them to do one eye, and then coach you through doing the second eye yourself. You are not obligated to buy anything - remember you are under fluorescent lights, and it's okay to look at yourself in natural light. Ask the rep for her card so you can return to her personally if you decide to purchase. It's okay to try a different counter on the next day, and do some comparisons (take a selfie if you want to!).
I agree that yellow concealer is ideal, but go ahead and try a few different counters. I'd go to a department store that has several competing companies rather than set my sights on a particular store.