So I'm not very good at installing on anything but Windows, but unfortunately I'm working with OS X Yosemite.
I seemed to have successfully installed the AirVPN Client because it's showing up in my "Applications" and it's in my dock but when I open it only asks for my Mac's password. However, there's no place for me to enter my AirVPN account username and password, nor is the option to pick the server.
What I did so far is this:
I installed the .pkg Package installer
on this page: https://airvpn.org/macosx/
for Using our client (OS X Mavericks, Yosemite ONLY)