Go to the AGH Panel and log in with your AGH e-mail credentials.
Select the "VPN AGH" tab and press "Enable VPN access".
Download the correct version of OpenVPN for your operational system at https://openvpn.net/community-downloads/ and install it with default settings.
Find the VPN certificate you have downloaded earlier from the AGH Panel, select it and press "Open".
Open the OpenVPN menu and select "Connect".