Install an Invasion & Guns 1.12.2 Modpack server through the Control Panel (Servers → Select your server → Game servers → Add Game Server → Invasion & Guns 1.12.2 Modpack)
The server went up fine, prices were great, but downloading mods came with some challenges. When I tried to put shaders on, the server would stop going up, and I had to take them off. Asking for support was very responsive and helpful, too.