How to put on a healthy amount of weight?

I used to be chubby now im pretty skinny, i went on a low fat diet with bunch of healthy and some fatty food and no junk food plus i work out around 5 times a week, this dint work out well because im a little too skinny, lately i been eating more "unhealthy food" (on purpose) and exorcising about 2 to 3 times a week rather than my usual 5 times, is this a good method to putting on some weight and the weight i want to put on is mostly muscle how do i achieve this? by the way im a 16 year old male.