microcontroller - How can I measure battery voltage with my MCU?

I am currently using the PIC24FJ128GA010 and I am planning to use Input/Output port to connect my 4.2 V LiPo battery and to check if the voltage value doesn't go below 3.7 V.

I am thinking to connect it to any of my input/output pin but I am wondering two questions:

1. Is it the correct pin?


2. Should I do a specific montage with resistor?