Eat high quality protein

Exercise training breaks down your muscles. Protein builds them back up. And the harder your lifting workouts, the more important protein intake is to your recovery.

Add supplements in your diet such as

Creatine
Creatine doesn’t directly build muscle. But by boosting your performances at high-intensity lifting workouts, the natural compound effectively promotes muscle growth.

HMB
A natural compound produced in the human body, beta-hydroxy-beta-methylbutyrate prevents muscle-protein breakdown, encourages muscle growth, and speeds exercise recovery.
Unfortunately, it’s hard to significantly increase levels through food alone.
HMB in tandem with a high-intensity lifting routine significantly improved muscle strength and size compared to lifting alone. Plus, in the off-chance that you push yourself too hard, HMB helps prevent the effects of overtraining—including muscle loss.

Take enough sleep

Muscle recovery requires more than the right nutrition. It takes time—roughly eight hours per night.
when you sleep, your body releases human growth hormone, which facilitates muscle growth and keeps levels of the stress hormone cortisol in check.

Increase the training time

your number of reps multiplied by your number of sets—is a primary determiner of hypertrophy (aka muscle growth). And to increase volume, you may actually need to go lower in weight than you might guess.
Compared to training for strength, intensity is going to drop during the hypertrophy phase of a program, with intensity sitting between 50 and 75 percent of the person’s 1RM, the maximum weight he or she can lift for one rep
To get the volume your muscles need, performing each of your lifts for three to six sets of 10 to 20 reps.

Decrease in resting time b/w sets

When lifting for hypertrophy, rest periods of 30 to 90 seconds encourage a quick release in muscle-building hormones (including testosterone and human growth hormone) while also making sure that you really, truly fatigue your muscles