If you want to see who is using your network, there are a few things you can do.
One way is to check your router's activity logs. Most routers keep track of which devices are connecting to it and when. So if you see an unfamiliar IP address or device name showing up in the logs, that could be someone using your network without your permission.
Another way to tell if someone is using your network is by monitoring your bandwidth usage. If you notice sudden spikes in internet usage even when you're not home or using the internet yourself, that could be a sign that someone else is on your network.
If you're concerned that someone might be using your network without your permission, there are a few steps you can take to protect yourself. First, change the password on your router so that only authorized users can access it. You should also enable encryption on your wireless network so that any data being sent over the air is protected from eavesdropping. Finally, consider investing in a good firewall software program to help block unauthorized access to your network.