I'm looking to start up a home workout. I don't really know much about how to organize a workout that suits me?

I'm 17, athletic background, natural runner/sprinter, but I weigh only about 145, skinny, but lean. I'd like to gain muscle mass, and still work on abs and cardio and stuff. I only have an exercise ball, medicine ball, chin up bar, and bowflex at my disposal. Could someone help me figure something out?