If you have fat on them you need to lose the weight. An effective way of doing this is adding cardio to your workout routine to burn off the fat, and eating well. If this is really important to you, count your calories and really focus on losing pounds of fat.
The second option is to make them bigger. Do this by working out with weights, doing 8-12 repetitions per set. This is the number of repetitions that is best for inducing muscle hypertrophy - an increase in muscle size. This will give you bigger muscles, along the lines of those that bodybuilders have, and the very act of weight training will give you more residual muscle tone. BUT no-one will see that toned muscle if it's covered with fat.
If you want more particulars on getting ripped check out this info about getting a six pack stomach. It'll help you slim down your bulky muscles.
I have bulked up more than slimmed down and I need some assistance with slimming down. I still worked out 5 or 6 days a week, eat a low calorie diet, while not doing any strength training and no longer having protein shakes. I am not able to slim down and lose weight. Although I have lost a few inches, I have not lost one pound in a 4 months period.
I think a good workout regimen will help. Though there should be a proper check on the diet you are having but doing cardio or any other hardcore exercises will help as well. One can also try plus size yoga as well.
YOGA is the best alternative to shed away that extra fat.