Om Namo Bhagavate Nityanandaya Mahamantra has no distinctions of gender, caste, creed, religion or even a yogi or a worldly being. As mentioned earlier, this Mantra is the simple way to lead a prosperous worldly as well as spiritual life, hence the way to chant is also simple. There are no rituals to it, like to sit in particular asana (pose) or to chant only after bathing or to chant a specific number only or to chant on a specific day. This Mantra is the very own form of Parabrahma which is ever illuminating within us, hence one can chant it anytime, anywhere, while in dhyana or pooja or working or walking or while sleeping. Nothing is considered unholy to chant this Mantra, be it any eclipse or demise in family or in sickness or in menstruation, this Mahamantra sanctifies everything and hence can be chanted anytime. There are no Gender differences, men, women, children, elderly, everyone can chant this Mantra.
Also, if you are new to this and you want to start with certain routine, maybe you could fix a time of the day or night, use a mala to count if that helps, maybe start with a specific number or certain duration to begin with.
Best way is to feel the Mahamantra, be one with it, take it in each breath while you inhale and exhale, it makes one go beyond the breath connecting to the Parabrahma. This way the Mantra becomes AjapaJapa, ceaseless chanting occurring effortlessly within one.
Om Namo Bhagavate Nityanandaya