Can anyone help me?

After the installation, when I had copied the code and uploaded config.php

I'm new on PunBB (I have used phpBB before) and I want to install it.
This is what I found at the documentation on this site:

Follow the instructions.

I followed all the instructions, but I get a blank page. Somewhere on this forum I've read that you need to CHMOD something.
But what do I need to CHMOD?

Why has the installation or documentation nothing say about it?