Can you tell me how could we cure psoriasis in ayurveda?

It is not possible!: Psoriasis is an autoimmune and strongly genetic disease. It comes in degrees of severity, virtually undetectable to very severe. Ayurveda has no studies supporting it in psoriasis!

Nobody cures it: It can be managed. I'd trust an evidence-based physician. If you are promised a cure through ayurveda, it probably won't happen. Remember psoriasis comes and goes. When it fails, the practitioner is likely to make an excuse. ("You ate GMO food.") There are comforting agents that a traditional practitioner may have for the skin. These can be adjuncts. Best wishes.