Arrange some nail polishes that match with American flag like blue , white, red with base coat, top coat to protect your nails and don't forget a toothpick to draw the stars.
First, cleaning your nails with alcohol to clean dirt and oil on the surface of your nails ( it may help your nail polish stick harder and long lasting than. If you just apply nail polish). Apply the base coat and background nail polishes.
During waiting for nail polish dry you can practice draw the star on your finger nails. Drop a drop of nail polish on you nail and use toothpick pull from center to 5 different sides. You can fix your stars by toothpick, it's up to you! After draw the stars on your nails, wait for they're "quite dry" and apply top coat on your nails.