STM32L4 Clocks Configuration
Download the STM32CubeL4 package, which includes example projects for your board and others.  The example projects will include code for setting up the clock and PLL.  There are pre-made projects for IAR EWARM, MDK-ARM, Atollic TrueStudio but you'll have to create your own project and port for MikroElectronika mikroC.

The STM32Cube example projects use ST's HAL and/or Low-Level (LL) libraries.  The library source code is included so even if you don't want to use the libraries in your application then you can still refer to the library source code as an example.