It will take a while because of the heat damage...or you could cut off the heat damaged hair. There are different methods to bring your hair "back to life", but the most reliable one is making sure your hair gets moisture.
Try a hot oil treatment, low-poo, and deep condition. Use a leave-in, then a soft hold product. Air dry only. You can also place a conditioner on your dry hair (don't mist or wet hair), rinse, cowash, deep condition. Use a leave-in, then a soft hold product, and air dry.
I've never had heat damage, but at one time my hair was so dry I thought it would never be soft again. These two methods helped me. You can also sleep with a satin bonnet for a while.
I'm sure other curlies will chime in--HTH.