How do i gain muscle?

Hi. I lost around 50 pounds since July till now and now i want to start gaining muscle such as abs, bi tris and bis. I used to run 6 miles and did some weight lifting when losing weight and ate around 1600 calories a day. Now i want to start gaining some muscle because my rib cage is showing and my man r gone! but i still have a little fat left on my stomach. What should i do to gain more muscle?? I was thinking about running 4 miles a day and some more intense weight lifting but i need advice!