Drag your VPN configuration file from your VPN to the big box in the PIC or click on open configuration file and load your VPN Configuration file. Some VPNs already have your username and password in that file when you got it from your VPN website. If yours does not after you’ve loaded the VPN config file you can click on the little gear above where you now see your VPN loaded and after clicking on the gear you can enter the username and password there and then click APPLY…
I’m using the Flint with FW 4.01 Beta2 as well and have mine configured for both Wireguard and OpenVPN but I use the Wireguard now that my VPN provider (Surfshark) finally has the config files for Wireguard with a router. Good luck.