HOW TO USE COMP1 in STM32 -LRWAN1 board

I used STM32-B-L072Z-LRWAN1 board and want to used COMP 1 and COMP2 in my project.to used COMP1 as per data sheet PA1 can be used as inputbut on STM32 LORA board its not incorporated.I want to know where PA1 is used ,any doc is useful.Can I used this pin/COMP1 separately in my custom board or not.pls help me out