[Galaxy S 5 Q&A, Help & Troubleshooting] CoreyOS:
I don't mean to sound patronising but it's just common sense to have Samsung drivers installed when using your computer to communicate with your device. (I did not thoroughly check through this guide but only linked it as I followed this before when I first began flashing custom firmware/ROMs to my devices myself.

Also, the google apps link is to get Google play functionality on Lineage OS as it does not come with any Google functionality whatsoever when installed standalone. This adds Google Play Store and Google Play Services to the ROM. You can install Yalp store from F-Droid if you do not wish to install Google apps but please note if you do decide to go without Google apps, you will not have contacts sync so you will have to export and import your contacts manually using a vcard file.

Apps that are dependent on SafetyNet and GPlay Services such as Snapchat also do not work without flashing the Google apps.

Also I only suggested Pico OpenGapps as it only comes with the bare minimum functionality to get Google Play Services running. It's up to you then what you install.

No, you do not need to root your device to flash anything via TWRP.

TWRP is used to flash root tools such as SuperSU or Magisk, it is the control panel to your hardware pretty much.

So...

Flashing TWRP:

1, Install Samsung Smart Switch or USB drivers (If smart switch doesn't work try these:

http://developer.samsung.com/common/download/check.do?actId=698)

2, Download Odin and the TWRP image for your device (Links in my OP)

3, Turn your phone off, hold Power + Home + Volume Down to enter Download Mode. (Follow instructions given on screen once download mode is active)

4, Plug your phone in via a reliable USB port and cable

5, Run ODIN as Admin and tick the AP box and choose the TWRP .tar file by clicking on AP.

6, Click Start at the bottom of ODIN and wait for the recovery to be flashed.

7, Now as your device reboots, hold Power + Home + Volume Up to enter your newly flashed TWRP recovery.

Optional ** If successful, make a backup of your original firmware using the backup section in case you need to get back to it in future.

Installing the ROM:

1, Within TWRP, go to Wipe > Advanced Wipe and tick "Cache", Data" and "System". (You will lose all app settings if you haven't backed up)

2, Go to Mount > Mount USB Storage and plug into PC in order to copy the rom, gapps and other files to your internal storage.

3, Unmount storage, go to "Install" from the main menu and select the ROM and flash it. (Use "add more zips" option to select gapps and others)

4, Once all has installed reboot and fingers crossed you'll see the Lineage boot animation :good:

Like I said yesterday, I take no responsibility, just trying to help out.

Hope you get good results.

It's not all bad if you device won't boot if something goes wrong, you can always just flash the original firmware via ODIN which is provided by Sammobile. (Been there, bricked that, fixed that etc etc)

Keep me posted! :)

---------- Post added at 11:14 AM ---------- Previous post was at 11:09 AM ----------

Forgot to mention, also Enable OEM Unlock I've noticed is only present in more recent devices. If you do not have that option and you have thoroughly checked it does not exist, you should not have to worry about it. (Please don't take that ass 100% gospel. I just noticed my Samsung J3 has it (2016 mid) and my S5 does not (2014 Flag)... Up to you, just do some digging but I don't have taht option and I have never been FRP locked... (Only on my J3 ;))