No, don't ever use Rom Manager to flash a rom. You need to do it manually through recovery. It's a bit intimidating at first but it's not difficult and it's something that everyone should learn to do if they are gonna flash roms. First you need a custom recovery like TWRP or CWM recovery. You can install TWRP with Goomanager on the Play Store. Once you have your custom recovery of choice installed reboot into recovery and flash from there.
It's always a good idea to make a backup first before you flash anything. After you make your backup image it's time to wipe your device in preparation for flashing your new rom. If you don't wipe there will most likely be problems with your new rom since there are old files that may conflict with the new. After wiping everything (except the SD storage of course) you can now flash your new rom. Once it's completed just restart your phone and wait for the new rom to load.
It will take a few min to load up your new rom the first time so don't freak out if it's sitting at the boot animation for more than the usual 30 seconds. After that you should be good, it'll take you to the setup screen to add your Google account and such. If it doesn't load then go back into recovery and try it again. If you get lost or don't know what to do next, feel free to come back here and ask. Most users on this forum would be more than happy to help you out. It's much better to ask questions if you are unsure about something rather than brick your device. Hope it all works out for you.
Sent from my beastly LG G2 using Tapatalk
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