how to execute the JTAG instructions?

hi

i am a starter.

i want to use the parellel flash to config the fpga.

but the boot address can't be changed.

some documents tell to execute the jtag instruction APFC_BOOT_ADDR to change the boot address

but i don't know how to execute the instructions.

i've created a .jam file,but how to edit it?

or ,the method is wrong?

i need your help

thanks