Installation of WP in Subdirectory in 1 and 1 Hosting space

Aim: wanted to have sub categories in subfolders

example.
domainname.co.uk –> have wp page (home page, with menu item as category)
domainname.co.uk/books–> have wp page for books home page & other pages
domainname.co.uk/pets–> have wp page for pets page & other pages

What I have tried till now
step1:
Installed 1 site with name “MAIN” WP in default directory of 1 and 1 hosting i.e. clickandbuilds
step2:
Moved to Root folder.
step3:
Change domain directy path point to root/MAIN
Now I am able to access the MAIN WP page(theam) using url like

Step 4:
domainname.co.uk

Step 5
Now created one more site called ‘Books’
all WP files got installed in side Books folder (i could see them)

Step 6
Move Books folder to Root/MAIN folder

Step 7:
Now I can access Books folder and its page thankyou.html
(which test html file i created)

With below url, I am able to access in browser like below

domainname.co.uk/Books/thankyou.html

Problem: I am not able to access install.php (i.e defaule WP installed file)

How to resolve this issue?