1st step: Standing straight up with your feet shoulder width apart or slightly wider than should width apart, bend your knees to lower your body as you simultaneously bend your upper body downward and slightly forward until you are able grab each dumbbell firmly with each hand and then lift yourself back into the standing position you started in with the dumbbells naturally resting almost completely in-line with the sides of your hips and thighs, but not too far back. This is the starting position. This is the beginning of the repetition.
If you are holding the weights to far back and your arms feel really uncomfortable, move the dumbbells slightly forward a little bit, but do not move them too far forward because when you do this exercise, if the dumbbells are too far forward, the weights will hit your thighs as you do the exercise which will cause you to do the exercise incorrectly.
2nd step: While keeping your back as straight as possible and your eyes, face, looking forward and level or slightly upward, breathe in as you lower your body as if you were about to sit down on a chair by bending your knees and lowering your butt as far down as possible while letting the weights move naturally downward past your thighs and knees while keeping the weights slightly behind or close to your lower legs without letting the dumbbells move in front of or hit your lower legs or knees so that you will maintain proper technique and stay more balanced as your butt gets closer to the ground. Remember to not let your knees go past your toes either. Also, do not look at the ground or let your shoulders go past your knees because if you do this, you will be arching your back to much and doing poor technique. If you lowered yourself correctly, your knees should be approximately making a 90 degree angle, or less, or much less, than 90 degree angle to the floor. At a 90 degree angle to the floor, your body should look like you are sitting on an invisible chair, and at angle much less than 90 degrees will look like you are about to sit on the ground, your butt will be much closer to the heels of your feet. Whether you stop at 90 degrees, or go all the way down which is a full squat, or somewhere in between, hold that position for a brief moment. This is the negative movement of the repetition. This is the middle of the repetition.
3rd step: From here, breathe out as you lift yourself back up to the starting position by extending your knees and standing up as you let the dumbbells naturally move back to their original position. But do not lock out your knees. This is the positive movement of the repetition. This is the end of the repetition.
Repeat steps 2 and 3 to complete the required repetitions for your quads for the day.
4th step: Once you have finished, slightly bend your knees to get closer to the ground and lean your upper body slightly downward and forward so that you can set the dumbbells back on the ground.