I don't think there is a way to do that with Energia libraries. You have to use TivaWare libraries.
For that you need to include:
and I think I am not missing anything (I don't usually use the compiler that Energia uses).
Then this depends on which launchpad you have. Is it the smaller one? If it is just use:
As an example for 80Mhz clock with the PLL, main oscillator with external 16Mhz crystal:
For more info check this out: https://sites.google.com/site/luiselectronicprojects/tutorials/tiva-tutorials/tm4c123-clock