As this is the Swyama Siddha Hanuman Mantra it doesn't have to be chanted for a fixed quantity of Mantra Repetitions for being able to use it. Specific worship and rituals and regulations about way, sitting down mat, and counting rosary are usually not suggested for chanting this Hanuman Mantra. https://www.youtube.com/watch?v=ufkmD95y7fE&t=32s