To get started, admins will need to download the latest version of the WHMCS Upsell Module by Monarx.
After downloading the file, admins should locate the document root folder on their system. The folder is usually located in the directory path:
/var/www/html/whmcs/modules, although it may differ based on individual setups.
To complete the process, admins can utilize their preferred file management tool to copy the downloaded file. Afterwards, they should copy it into the document root folder.
After the user has successfully copied the file to the document root folder, they will need to extract its contents. This step is necessary to
unzip the module or add-on and create the corresponding directories for its files.
Move the above folders to the installation location of WHMCS (example /home/whmcsinstall/public_html/