Default Question about Installing a New ROM

I'm really confused about what to do before flashing this ROM: http://forum.xda-developers.com/show....php?t=2694471

I'm coming from CM11, I don't know what to do when it says "so basically just FULLY wipe". Does this mean to just factory reset, or can somebody tell me which boxes to tick in TWRP (System, Cache, Dalvik Cache, etc.) I'm worried that factory resetting will delete internal storage, because I have accidentally deleted internal storage before while flashing a new ROM, and it was a nightmare.

Thanks in advance!