How to install Vservs API into youre WHMCS:
Upload the files to you`e WHMCS ftp folder path /whmcs/modules/registars/vservs (module name: vservs)
Into youre WHMCS go to Setup > Product/Services > Domain Registrars
In the drop down menu: Select Vservs
Sent us an E-Mail with you're webserver IP address, then we will activate you're API access
Fill in youre Vservs-CP username
Fill in youre Vservs-CP API KEY
Press Save Changes an press Go
You can find de Vservs-WHMCS-API module here