I Want to Improve Muscle Definition

Answer:

Glad to hear you are taking an interest in building up your upper body to match your lower body. Balance is extremely important in physical fitness and you're definitely on the right track.

There are many exercises you can do in your own home to start building yourself up. Some exercises I would suggest for you to do would be as follows:

Chest: push-ups, dumbbell bench press, barbell bench press (if you have a barbell)
Arms: incline dumbbell curls, bench dips
Shoulders: dumbbell laterals, dumbbell shoulder presses
Back: one arm dumbbell rows, barbell rows

I would recommend you do 2 sets of one of the exercises for back, chest, shoulders and arms three times a week.

Back - 2 sets of rows
Chest - 2 sets of push-ups
Shoulders - 2 sets of presses
Arms - 2 sets of bench dips (do curls the next time)

A good way to arrange this would be to do this Monday, Wednesday and Friday.