I am trying to gain 10 pounds, what is the best(healthiest) way to do this?

Protein and weights: Weight bearing exercise, and eating plenty of lean protein (about 2.5 g/kg of body weight). If you have problems eating that much, whey powder is generally a good way to increase your ingestion. But make sure you get it from a reputabile source. Avoid creatine, and other "mass building" supplements. At best they are ineffective, at worst they can be dangerous as they are unregulated by the fda.

Why?: Why are you trying to gain weight? How tall are you and how much do you weigh? It would be a good idea to consult a doctor to check on the advisability of gaining weight.