Install OpenVPN GUI from official site
Login to Metahuman VPN Portal. Select 'VPNs' (A), your plan in question (B),
then 'Downloads...' on the left. Select your connection, or the complete .zip (D.)
Importing into OpenVPN and connecting
Since you now have OpenVPN-GUI installed, you can use these .ovpn files.
Right-Click on the OpenVPN icon in your taskbarand select 'Import file...' (A.)
Then, select your connection profile. (B.)
Click 'Connect' under the name you imported back down in the OpenVPN taskbar menu
Enter your credentials
OpenVPN is now connected.