How do I flash and prepare an ASUS Zenfone 2 Laser for custom ROM installation? I am tired of the original ROM on my phone and I'll install the resurrection ROM. 

I have the zip, but if I am not wrong I need to first do 3 things:

-get root access

-install TWRP

-and adb

Am I right?

I am still in the process of understanding how it works.

Where do I get these files and instructions? 
I have found some links, but none of them seems to be easy and well-explained.

Thanks!
You don't need root access on your stock ROM. The step is:
     1. Unlock your phone ROM using official APK or other means (ASUS unlock APK was known to be buggy)
     2. Install TWRP using ADB
     3. Flash custom ROM using TWRP

Your warranty will be void and you might get your phone bricked.

Detailed guide: 


Install ADB on your PC c:\adb
Copy TWRP recovery and ROM zip file to adb folder
In your Phone set development option on, enable USB debugging
Unlock your phone using official ASUS APK 
Connect your phone to PC, run cmd on c:\adb ".\adb devices" confirm device connected
Run cmd: .\adb reboot-bootloader
Run cmd: .\fastboot devices, confirm device connected in fastboot mode
Flash TWRP: .\fastboot flash recovery twrprecoveryfile
Enter recovery mode
Flash custom ROM using TWRP