Please download bug fixes regularly by going to System -> Updates, then click Install Update (For your current version). Alternatively, activate Automatic Bug Fixes in System Settings.
Make sure you have set up Cron in your control panel to run at least once a day. This is very important and required for automation.
It's very easy to install Hosting Billing.
You upload the zipped file that you downloaded from Codecanyon to your server.
Unzip the archive and you will see 3 folders in the unzipped folder
These folders are documentation, hostingbilling-new-installation and hostingbilling-update
Open hostingbilling-new-installation and select everything inside, then copy or move or drag to public_html or whichever directory you was to install in.
Create a new database (It must be empty)
Open your URL and the Installer will start.
Just follow the steps on your screen and provide the required information to complete installation.