Commands to calibrate internal RC oscillator where no softdevice is used

Guys, i'm using a custom board with nrf52832 on it. The custom board doesn't have an external oscillator. So i'm trying to use internal RC oscillator. I am not using any softdevice. So, I need help in the commands needed to write in my program in order to make use of internal RC oscillator . I am trying to use an example similar to proprietary RF.