Two questions about my new My Book 8 TB

Yesterday I purchased a WD My Book 8 TB hard drive. There are two questions I have about it.

First, it is generating a thumping sound every few seconds. It’s quiet, but when no other sound is happening, that thumping sound is very irritating. Why is it doing that? Is there anything I can do to stop it?

Second issue. How in heck do I access it? I’ve connected it to my Synology router. I’ve gotten into the router, enabled Windows File Service. It gave me a URI to access it in Windows 10 File Explorer. I tried, but then Windows Security pops up a window asking for my network credentials. What is it asking me for? This is a simple, peer-to-peek network; it isn’t an Active Directory network. I’m using this My Book in a home environment. Just a Windows Workgroup type of situation. For any machine to access any other machine we’d use our Microsoft account. I’ve tried using that, but that immediately rejects it. So, I have no idea what this is asking me to provide, so could use help, please.