Using OpenVPN GUI
When OpenVPN GUI is started, your config folder (C:\Program Files\OpenVPN\config) will be scanned for any .ovpn files, and an icon will be displayed in the system tray.
When you want to connect to a network, right-click the OpenVPN GUI and click connect. If you have more than one config file you will be able to choose between them. If you use a passphrase-protected key you will be prompted for the password.
OpenVPN GUI can start a connection automatically when it runs. To enable autoconnect simply add this string to the command that starts the OpenVPN app:
--connect client1.ovpn
In Windows, you'll need to append it to the following registry key:
OpenVPN Startup.reg (right-click, save, and run)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run openvpn-gui = C:\\Program Files\\OpenVPN\\bin\\openvpn-gui.exe
Change client1 as needed for the name of each client config file.