Get on a high pulley machine with a wide bar attachment and choose a moderate weight. (fitnessandpower.com)
However it is not easy to find the right cable pulley machines with high quality for your garage gym if you don't have much experience. (garagegymbuilder.com)
The main advantage of performing it on a cable pulley machine instead of using a barbell or dumbbells is that the machine allows you to work your bi's throughout the entire range of motion, thus causing more hypertrophy. (fitnessandpower.com)