You will have do the configuring in the BSP gpio.h file. On page #42 of the "Digi Connect ME-9210 Hardware Reference" manual you will find the needed configurations.
According to the module's pin-out chart, pin #9 (RTS) is mapped to GPIO and pin #11 (CTS) is mapped to GPIO
Link to the ME-9210 Hardware Reference Manual:
I hope this document helps.