Gaining muscle

i am six foot tall weight a low weight of 142 and sometimes 134 after i am done running, i have a old bench that has a cable pulldown, benching bar and i need a workout to get me to gain some mass cause my sternum sticks out and i have tried some workouts that arent working cause i am no bigger and my arms are only 14 in. and my waist is a 27. Have any suggestions for a workout?