I am new use to Vtiger CRM. I need Entity Module. I use to https://community.vtiger.com/help/vtigercrm/developers/extensions/examples/entity-module.html#expenses-php. But, I can't find bootstrap vtlib script in root folder of Vtiger to activate the module entry.
The documentation clearly says to create that file and put it in root folder.
Create new file, name it what ever you want for eg: new_module.php and write code for new module as in the documentation
Run the script once like http://yourcrm.com/new_module.php. It will register the module and its field details in database. You might require other supporting files like module class file language file in appropriate locations
There is another easy way to create modules in vtiger using vtiger console script. you can read how to create modules using console app from this url
https://lajeeshk.com/quickly-create-vtiger-modules-in-seconds/