The practice is described as calling the buddha to mind by repeating his name, to enable the practitioner to bring all his or her attention upon that buddha.This may be done vocally or mentally, and with or without the use of Buddhist prayer beads. You can practice for a set amount of time, 10, 15 or 30 minutes a day or a certian amount of time 108, 500, 10,000 a day, etc. Recite or chant Namu Amitabul as much as possible no matter where you are, internally or out loud.
When Namu Amitabul is recited, and the mind is emptied out after each repetition. When idle thoughts arise, the phrase is repeated again to clear them. With constant practice, the mind is able to remain peacefully in emptiness, culminating in the attainment of samādhi
You can alos listen to the buddha's name, here are a few versions:
Namo Amitabul Represents: The most beautiful greatest true compassionate powerful golden light from the universe’s energy.