Drag Viscosity onto the application icon to install.
Enter your Mac user password.
Go to applications and start Viscosity.
On the question on if you're sure about open the file, click on "Open".
Click on the Viscosity icon and select Preferences...
Download the configurations files for OpenVPN here: PrivateVPN-TUN.zip
Extract the files some place on your hard drive.
Click on "+" -> Import Connection -> From File...
Browse to location were you saved configuration files and select privatvpn and then click Open.
Click on the Viscosity icon and select a server you want to connect to.
Enter your user name and password for PrivateVPN.