There are two modes:
Download CPlugin.WebAPI.Realtime.ts typescript interface file to get all interfaces and classes used.
Feel free to check source code of pages below to get general idea about SignalR/WebSockets connection.
simple example can be found here.
MT4 SignalR example, download it, put correct settings and run on your own
MT4 SignalR streaming example, download it, put correct settings and run on your own