Hi,
good starting point is SDK documentation - you can find it in c:\NXP\S32DS_ARM_v2018.R1\S32DS\S32SDK_S32K1xx_RTM_3.0.0\doc\html_S32K144\ folder. There is also SDK Example:
You may also find helpful this thread - https://community.nxp.com/thread/479473
Jiri