If you want to identify a device on your Wi-Fi network, there are a few different ways you can do it.
One way is to look at the list of devices that are currently connected to your router. Most routers have a web interface that you can access by typing in the router's IP address into your web browser. Once you're logged into the router, there should be a page that lists all of the devices that are currently connected. This will show you the MAC address, IP address, and other information about each device.
Another way to identify devices on your Wi-Fi network is to use a tool like Wireshark. Wireshark is a packet sniffer that can capture traffic on your network. When you run Wireshark, it will show you all of the traffic that's happening on your network in real time. You can use this to see what kind of traffic each device is generating and narrow down which one might be causing problems.
Finally, if you're having trouble with a particular device on your Wi-Fi network, you can try using its MAC address to block it from accessing the network altogether. Most routers have an option to blacklist MAC addresses, so this can be a good way to deal with troublesome devices.