Hi,
In the following link, you will find the Get Started with the LPC55S69-EVK I suggest you check it.
Get Started with the LPC55S69-EVK | NXP
Regarding the sdcard examples, you can download MCUXpresso SDK for the LPC55s69 from the following link:
https://mcuxpresso.nxp.com/en/builder
After download it, you will find some examples that you can use as reference.
I suggest you, download the API documentation

I hope this helps, have a nice day
Regards
Soledad