The method to block devices connected to your WiFi may vary depending on the type of router and its configuration. Here are some general steps that you can try:

Access your router's admin panel: Open a web browser and enter the IP address of your router in the address bar. The IP address is usually printed on the router itself or can be found in the documentation that came with it. Once you enter the IP address, you should be prompted to enter your router's username and password.

Find the list of connected devices: Look for a tab or section in the admin panel that lists the devices connected to your network. This may be called "Device List," "Client List," or something similar.

Identify the device you want to block: Look for the MAC address of the device you want to block. The MAC address is a unique identifier for each device that connects to a network and usually consists of six pairs of alphanumeric characters separated by colons.

Block the device: Once you have identified the MAC address of the device you want to block, look for an option to block or restrict access to that device. This option may be under the device's name or MAC address, or it may be in a separate tab or section of the admin panel.

Save your changes: After you have blocked the device, make sure to save your changes and exit the admin panel.

Note that blocking a device from your network will prevent it from accessing the internet, but it will still be able to connect to your WiFi network. To completely remove the device from your network, you may need to use a different option in your router's admin panel, such as "Disconnect" or "Forget."