M21 Need workout advice - Underweight 130lbs, Skinny, for all my life.

To start I’m 21, I mostly run, I haven’t been good with weights and always lose motivation. I’ve always struggled to maintain a healthy weight. I’m 130lbs and skinny. Always never eating enough and losing appetite.

I want to build muscle, and look more like a man. Where do I start?

Please help, I want to make a change in my life.