Do you mean a WiFi connection from a device such as a PC or phone, or do you mean WiFi from a router.
Without a lot more detail about exactly which WiFi you are talking about, and in the case of a PC, phone, etc, what operating system it is running, it is not possible to give detailed instructions.
The catch-all answer is to turn off your router and shut down all your devices, but I doubt whether that is really what you want.
Now, perhaps you will EDIT your question to update it with the missing detail.