You must first know the IP address of the user;

Log in to the relevant router and use the show arp command to view the MAC address corresponding to the IP address.

Use show mac-address-table to check the port corresponding to this mac address and determine the switch corresponding to this port.

Log in to this switch and use show mac-address-table to check the port corresponding to this mac.

P/s: Huawei series equipment seems to use display instead of show；; Some switches use fdb instead of mac-.