The packages add JellyBridge to your app menu (Start menu on Windows, Applications on macOS). From a terminal, run jellybridge.
On the first start there is nothing to set up: JellyBridge opens straight on the server screen. After you sign in once, later launches go directly to your Home screen and show it about a tenth of a second after the window opens, from the copy saved last time, while the server's latest version loads.
If it will not start
JellyBridge needs a graphics driver with OpenGL 2.0 or newer. If yours lacks it, JellyBridge shows a message saying so; install or update the driver. Started from a terminal, it prints the reason there too.