If you have severe dandruff then yes you should wash your hair everyday or at least every other day to remove the dandruff and keep your scalp and hair healthy.
When washing the dandruff out of your hair it's recommended to use a medicated dandruff shampoo which can help heal your scalp and prevent further dandruff from occurring.
You should use a moisturizing conditioner after using the medicated dandruff shampoo to help keep your scalp moisturized.