If you start yoga, your metabolism becomes quite efficient. More than weight, perhaps you need to focus on gaining muscle tone and stamina which yoga promises. Also, agnisara kriya increases appetite and is recommended for those who wish to gain weight. You will find instructions easily enough on the net on how to do it, though again it is best learnt with a yoga instructor. Also, the yogic injunction to focus on having a large breakfast as the biggest meal of the day will help you there. According to yoga, you must eat breakfast like a king, while dinner must be like a beggar. Try this also. Perhaps you are skipping breakfast. Also, if you know of good yoga instructor you may ask him/her to teach you chandra bhedana pranayam (cooling pranayama). This is an advanced pranayama and best taught by an instructor. Plus, you can drop in at Landmark bookshop (or other shops stocking Bihar School of Yoga books) and see this book Yoga for Perfect Digestion by the Bihar School. It has a list of practices that you may attempt from yoga for real and healthy weight gain.
