First, Rabelais was a monk of the Franciscan Order, so reading the Rule of St. Francis would be a great help.
Also, you ought to know something about the Tridentine Mass and the Divine Office.
The general life of the average Franciscan monk hasn’t changed much over the years. Monks would rise before sunrise, and sing the first parts of the divine Office, Matins and Lauds. From here on, the time of day and the singing of the office is measured according to the Old Roman way of measuring time. After Matins and Lauds, Prime, or the first hour, would be sung around 7 a.m. At 9.a.m., terce, or the third hour, was sung. Sext, the sixth hour, was sung around noon. Sometime in the morning, the monks would go to mass. Some of the brothers would be ordained priests, making the community entirely self-sufficient from a religious point of view. In the afternoon, None, or the ninth hour, was sung at 3 p.m. Then at dusk, Vespers, the evening prayers, were sung, and after dark before bed, Compline, the last hour of the office. Note that recitation was communal, and usually sung (chanted), not spoken. With all this office singing, the Brothers would have prayed all 150 psalms every week.
Brothers would also say other prayers throughout the day, such as the rosary. Back then, there would have been 3 sets of mysteries of the rosary, and the day on which each mystery was said corresponded to that day’s offce. Brothers also sometimes practiced what is called Lectio Divina, a way of praying while reading and studying the bible.
In addition to prayers, the office, and Mass, monks would have done physical labour. This is sometimes different based on the individual. Some might have worked in vinyards, or maybe done carpentry, and some would still have copied manuscripts in Rabelais’ time. Some monks would also be sent on missions to preach in other countries, spreading the word of God.
Finally, note that all the Brothers would have been Celibate, and voluntarily poor. To show how serious they were the oath of poverty, the Capuchin Friars, a reformed sub-division of the Franciscans, are not even allowed to touch money. No Franciscan may own personal property.
Bear in mind that it’s much more complicated than this, and monks often engaged in teaching, preaching, and all sorts of other duties.
Mat.