Download the game here
Run ZClient, drop game exe or lnk to zclient. Also you can make lnk to game and add full path to zclient with exe like this: "D:\ZClient\ZClient.exe" "D:\Starcraft Remastered\x86\Starcraft.exe".
If you create a game behind router – set up port forwarding 6112, TCP & UDP. If it’s not Public IP (depends on your provider) – you can only connect to other peoples games.