problems with connecting a second computer to my network

Version 21H2 (OS Build 19044.2604)
I have virgin media and a WDMYCLOUD storage device connected to the router in my home.
They have been working fine and I can store files on the 'network drive'.
I recently connected a second computer to the network, or at least got it to see and use the internet.
When I look at either computers windows explorer and click on the network section it shows two computers, the second one I have just added and the wdmycloud storage device.
In media devices it shows the first computer (the one I have always been using)? see the second question.
In Network infrastructure it shows the router and in storage it shows the WDMYcloud storage device.

If I click on the second computer icon in windows explorer in the first computer it opens a box that asks for Network credentials, asking for a user name and password, I wasn't aware I had a network credential? What does this mean?
If I click on it in the second computer it shows no files?

I am going to ask multiple questions in the hope that one solution might fix them all.

In both the first and the second computer explorer pages clicking on 'network' down the left side I see the first computer under 'media' instead of 'computer'. If I click on it in either computer it opens media player and tries to play it as a media file? Is there any way of moving this to 'computers' where I assume it should be?

Start by looking at the IP info on that second computer to make sure it has the firewall set as Private and same Dns and DHCP server i fo as the other computer.