A few base steps to follow…
Website1 = Main website
Website2 = Duplicate Website
Step1:
Copy all Website1 files.
Step2:
Paste all files into new(duplicate) directory(Website2).
Step3:
Install Wp Migrate DB on Website1.
Step4:
Export the website database using WP Migrate DB(See Step3) – This includes some sub steps in order to update base url etc. – See WP Migrate Documentation – Very simple
Step5:
Create new empty database in phpmyadmin and import the database you exported in Step4.
Step6:
Open the wp-config file of Website2 and update the database details to connect to the database you created in Step5.
In short that should do the trick.
