PureOS/Purism on custom iMX6 hardware

Hello everyone!
I would like to know where/if it is exists a guideline to install PureOS/Purism in a custom board I have already done (actually it runs Debian Stretch ARMHF). …And if it is possible, what are the keys to developing a custom application running at boot. The board has resistive touch screen and the TSLib can be used. And it sports an internal eMMC of 4GB. The audio codec it is the SGTL5000 from NXP. The running kernel is a stock vanilla kernel 4.12, the bootloader is BareBox https://www.barebox.org/
Do you need some other info?

Best regards,