How do multiplayer work?

[Heraculas]

If it requires some fiddling about, is there a video guide or something someone can direct me to. Thanks.

[Dgo]

It's a bit complicated and assuming that you are the host client and you both must have the same emulator, same rom version, open ports, etc everything in sync.

Thus you have better and easier options with the excellent parsec or steam's remote.

[Fili]

Some cores do not have online functionality whatsoever. Check this guide to know which cores can be played online.

https://steamcommunity.com/sharedfiles/filedetails/?id=2654167744

[Heraculas]

thanks!