I'm confused!
As it was originally manufactured, your PC didn't have a wireless card fitted inside it. So, unless someone has since added such a card to it, it can't connect to wi-fi. (i.e. it needs a a wired, 'Ethernet', connection to a router). So a wi-fi password would seem to be totally irrelevant here!
Other than the mains power, the only lead to a wall socket that might be needed for a PC is an Ethernet cable to link it to a router. (An Ethernet cable looks like this:
https://media.cablesandkits.com/p/PC5BL02EZa.jpg . They come in different colours though, with yellow and orange both in common use).
A computer that's physically connected to a router with an Ethernet cable doesn't need a password. As long as the router itself is connected to the internet, the computer will also be as soon as the Ethernet cable is plugged into it.
So I'm uncertain as to whether you're trying to use a wi-fi connection (which, if there's no wireless card inside the PC, will be impossible) or an Ethernet one.
Start by checking that the Ethernet cable (if that's what it is) is properly plugged in at both ends. If it is, ask the manager to switch the router off for a few moments, while you also switch the PC off. Then turn them both on and try connecting again. If you still can't connect, you might need to try resetting the TCP/IP stack on the computer. (Don't worry! It's a LOT easier than it sounds!
https://grok.lsu.edu/Article.aspx?articleid=19483 ).
If that doesn't work, it could be worth ditching the Ethernet connection altogether and plugging a wifi adapter into a spare USB port. (e.g. one of these:
https://www.ebay.co.uk/itm/600-Mbps-5ghz-USB-Dual-Band-Wireless-Adapter-WiFi-Dongle-802-11-AC-Laptop-PC-UK/254630546618?hash=item3b4929ccba:g:oHcAAOSwBDle7le7 ). You'd then be able to connect the computer wirelessly.
[Just an afterthought: If the computer
has been fitted with a wireless card, you might be creating a conflict by having it connected to the router via an Ethernet cable at the same time. Try disconnecting the cable]