There is a Risk in installing a Custom ROM on Android because if you commit mistake by installing your New Custom ROM your phone will be Bricked or it will just start on the logo screen (Boot Animation)
it is because there is something wrong in installing or the ROM you have downloaded are not compatible or not for your devices that is one of the most Related Reason.
"Fix Android Bricked First AID"
THINGS YOU SHOULD KNOW
You need to INSTALL a Custom Recovery like (Twrp,CMW,ect)
Before installing your Custom ROM your Battery should be at 60% or Above 70% because it cause a couple of time in installing a ROM, if your phone will be powering off because of empty battery and the ROM Setup is not yet Finish the phone will only boot in Booting Animation , you need to finish intalling it first
It's Doesn't matter if your Devices is Rooted or not , you just need a Recovery mode like Twrp,Cmw to install it
If you are using Computer or Laptop to Manually install the ROM you need to Download Odin
You don't if you are now installing you ROM you don't need Internet connection anymore
OR FOR LOWER RISK YOU CAN JUST UPDATE YOUR PHONE TO THE LATEST VERSION