READ AND WRITE IN PIC32MZ2048 PROGRAM AREA MEMORY

Hi,
 
I designed a custom PCB for a datalogger application based on PIC32MZ2048.
 
At the moment I am programming a bootloader for my application. I use the application provided by Microchip to do the update. For now, this is done via UART.
 
The PCB has no switches to force the bootloader to start. To trigger the bootloader I have thought of recording a known data in a specific position in the PIC32 memory from the main application. At startup, the bootloader checks this memory position, if it is correct it continues with the update, otherwise it jumps to the main program.
 
How can I write to the flash memory of the PIC32? And read?
 
Thanks for your help.