The easiest way is to create a new project for your device in MCUXpresso IDE and then re-add your application sources.
You will need to port them to some extend as you won't keep that kind of C++ style of code: transform that into normal structs and functions in C.
The usage of the Arduino Wiring library can be replaced with calls to the MUCXpresso SDK. Or you can use Processor Expert if you like. I ported projects that way usually in less than a day, but that requies good knowledge of the Wiring library and the MCUXpresso SDK.
I hope this helps,
Erich