People keep telling me i'm too skinny. what is the best and quickest way to gain weight?

Combination: Eat healthy foods that are high in calories. Eat six meals per day. Work on strength training to build your large muscle groups. Work out with heavier weights with fewer repetitions. Sleep at least 8 to 9 hours per night. Hydrate well with water. Snacking when you are trying to gain weight>. Nuts are high in calories, contain protein & are high in monosaturated fat (almonds). We all should aim.