I am enrolled in the brown scapular, and I am wondering how I obtain the permission to just say 5 decades of the rosary instead of the Little Office of the Blessed Virgin Mary? Is there a prayer, or something I need to take when I go visit my priest?
It is no longer a requirement. What is asked for is a participation in some way in Carmelite spirituality. The most recent and authoritative catechesis on the Brown Scapular is this, issued by both Orders of the Carmelite family:
As per their Catechesis, this spirituality consists of, but is not limited to:
frequent participation in the Mass and reception of Holy Communion;
frequent reading of and meditation on the Word of God in Sacred Scripture;
the regular praying of at least part of the Liturgy of the Hours;
imitation of and devotion to Mary, the woman of faith who hears the Word of God and puts it into practice;
the practice of the virtues, notably charity, chastity (according to one’s state of life), and obedience to the will of God.
There is no more requirement to say the Little Office or to have it commuted.
Read this invaluable document. Because the Scapular is a Carmelite habit, the Carmelites’ word carries the day. It describes a proper devotion and use of the Scapular. What the Carmelites want is for the garment to serve as an aid to devotion, a symbol of our sharing of spiritual goods with the Carmelite family and a sign of our entrustment—a persistent prayer in a way—to our Lady’s maternal care.
Thank you for posting that. I would add that CDWS restored “custody” of the Brown Scapular including the responsibility for catechesis back to the Carmelite Orders over 20 years ago. The information you cited is indeed the authoritative norm for the Scapular.