Step 1 - Login to your xenForo Admin Panel and go to following location :
xenForo Admin Panel -> Home -> Add-ons -> + Install Add-on
Step 2 - Browse and select : addon-adiinviter.xml file from the AdiInviter Pro package files.
Step 3 - Click on Install Add-on button.
Step 4 - Now from the top navigation menu of your xenForo Admin Panel, click on AdiInviter Admin Panel menu.
The AdiInviter Pro installation will start. Simply follow the instructions on screen and finish the installation process.
Step 5 - Once you see the message Installation Complete, remove the installer files and folders located at following location on your server :
Note - Don't forget to remove the adi_install/ folder entirely from your server.