I scalded my arm a couple days ago, and now it has popped skin blisters. What should I do now?

Normal reaction. Blistering is a normal consequence of a so-called "second degree" burn. You don't have to do anything special, but if the blisters are large, you can clean a needle with alcohol and nick them to let the fluid out. (this is painless as the blistered skin is dead.) apply wet soaks with warm tap water a couple of times a day, and if you see any sign of infection (firmness, swelling) see your doctor.
Burns. Silver sulfadiazine (inn, or silvadene) is a topical sulfonamide/silver[1] antibacterial used as a topical burn cream on burns, including chemical burns. It prevents the growth of a wide array of bacteria, as well as yeast, on the damaged skin.