Hi Daniel,
you can use MCUXpresso Secure Provisioning Tool. In the documentation, chapter 6.2, you can find step by step how to boot from different memories.
Shortly, for booting from SD card, you need to build the application to RAM. During booting, ROM bootloader will copy the application from SD to RAM and start the application.
There is also community page "MCUXpresso Secure Provisioning Tool", so I'd recommend to send additional questions there. "RT"s and "MCX"s are different series.
Regards,
Marek
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