So, the Lord Buddha announced that the monks had to stay in the temples during the Buddhist Lent, the new monks studied Dhamma from the senior monks, and the senior monks taught Dhamma and the monastic disciples to the junior monks.
Not only that, the senior monks had to plan what they would do after the Buddhist Lent, where they would go to spread Dhamma, and how they could improve their Dhamma teaching to be appropriate to places and social, etc.