Hi welcome to HCM Dear , We lose weight or gain weight on each body part depends entirely in our genetics. But, we can target muscle mass gain on specific body part by doing weight training.To build up muscles of hands and legs only through exercise is not easy . Directing your body to gain fat in a particular area is impossible, because your body has a set pattern for weight gain . Adding healthy calories to your meals and snacks, as well as spending focused time at the gym ,Focus on your arms and legs by performing two to four exercises for each muscle group during each session of the two- to three-weekly workouts. Arm exercises include hammer curls, preacher curls, concentration curls, triceps dips, overhead extensions, pullups, pushups, flyes and triceps kickbacks. For your legs, appropriate moves include squats, lunges, step ups, leg presses, calf raises, dead lifts and leg curls. If you re just starting a program, use your body weight or the minimal weight for just one set of eight to 12 repetitions. As you become stronger, lift heavier weights that fatigue you, in four to eight repetitions for each of the two to three sets. help you balance your frame. Up-hill running builds the quad and calf muscles; Swimming and stretching exercises of legs and hands , helps you gain muscle and burn fat . Massaging your limbs with olive oil strong hands will further help accelerate the process of gaining muscle . Eat more protein in natural form . Protein is filling and good for maintaining muscle tone. Make sure to include nuts , cheese ,butter , milk . nuts ,dates with milk ,banana in your diet. Add daily servings of fruits and vegetables which provide you with dietary fiber, which can help reduce the amount of fat that your body stores. To gain weight, you must create a calorie surplus, which means you need to eat more calories than you burn. Consuming 250 to 500 calories more than what you need daily to maintain your weight will encourage muscle mass growth. . Drink lots of water to detox your system . You should be drinking 8-10 glasses per day. Water not only helps flush out accumulated toxins in your body, but also keeps your skin hydrated, smooth and glowing in summer. Results will take time. A lot of people with really good intentions and strong discipline quit , just before they start to see results. Get adequate sleep of seven to nine hours per night and optimal hydration to support exercise and a healthy diet for muscle gain. Consult a dietitian for right program of diet for muscle gain Slow and steady wins the race. Perseverance overcomes mountains . Results will take several months to become evident. So don t lose heart . All the best . Take care . Hope this helps solve your query