Read the chapter that matches the date*. For example, on the 15th of the month, read Proverbs 15.
* This reading schedule divides Psalms into 30 readings and Proverbs into 31 readings. Since the months differ in length (28, 29, 30 or 31 days), at times you will need to adjust your reading schedule at the end of the month. You might read a "double set" of chapters at the end of shorter months, and when the months have 31 days, you will not have a set of Psalms to read on the 31st day.
Following this reading plan will allow you to gain wisdom that you can apply to your life.