fat isnt good, its unnatractive and it makes you smell and unhealthy, however look into bodybuilding, this way youll increase lean body weight (muscle), look more attractive and be more halthy
eat ?
if you want to gain fat because your skinny and you think there is a health risk being your current under weight, then you shouldn't be gaining fat fast.
Ask most of the ppl in this country i'm sure they know... or consume tons of protein.
I respect your enthusiasm, but you really cannot get fat relatively that fast. But you can increase your amount of calories each day, do weight training, and cut down on cardio a little. You want to consume a lot carbs like potatoes and also you need to get a lot of protein from eating peanuts and lean meats. You could also drink nutritional supliments (Ensure, Boost) they worked very well for me. Goodluck, it takes hard work both gaining and losing weight so you seem like a very strong-willed person to consider gaining.