Playing missions on imported Maps

[PaxtonMega 1]

Hey BIS Friends and Modders around, I wondered how it would work to get to play old missions on old maps that are importable. I managed to get Weapons and Vehicles of Chernarus and Takistan alongside the maps into the game and fiddled around in the editor. Sadly I didn't find Chernarus in the "Host new session" tab under multiplayer. Does anyone of you know how to get that running maybe? Saw videos of peeps playing together in Chernarus or even on Taviana. Maybe I am just too dumb to use the Search Function correctly and it's allready on here. Please help me out :)