Hello,
- I recommend you refer to the clock diagram to configure the Clock :

- The another method is you can create one KSDK+PE project, then you can directory configure the clock
on the fsl_clock_manager component :

- Please pay attention that About this chip , only on the high speed run mode , the core clock can up to 100MHZ .

while in the High speed run mode , Flash programming / erasing is not allowed .

Hope it helps
Alice