Monthly payments are due one month post your loan disbursement date each month. If that date doesn’t exist in a particular month (e.g., the 31st), the payment will be due on the last day of that month.
For example, if your loan disbursed on August 31st, payments will be due on the 31st of each month. In months without 31st day, such as April, your payment will be due on the last day of the month (e.g., April 30th).