Welcome!
The "connection.php" is a main file that establishes connection with the database, so before starting php file make sure the password and users 
are updated correctly.
In all the php file the database used is "post" and table name was kept "posts"
To run this site just download the files and on any software like Xampp run the local server and create the database "post" and table
"posts" and keep a field "id" which is meant to be the primary prefferably auto_increment to reduce the chances of error.

Disclaimer!
The site doesn't have a setup for indentifying users and defining powers but the same can be done with some modification in Login page making
it eqquiped with php;