Hi Jurij,
You can find some SPI Sample codes following this path.
C:\NXP\bstudio_nxp\sdk\JN-SW-4170\Platform\DK4\Source\LcdDriver.c
C:\NXP\bstudio_nxp\sdk\*SDK NUMBER*\Platform\DK4\Source\LcdDriver.c
You can use another flash, but be sure that the flash support the SPI protocol and the voltages that de JN supports.
Best Regards,
Mario
Ok found it, thank you