Do I Need A Microsoft Account On Windows 10?

Bought a used computer for my kid. Tried to set it up and it took me directly to a page for setting up a Microsoft Account. But it won't let me use my cell phone number as part of the set up because I have that phone listed on my account. We don't have another cell phone and I won't get one for my son, as he is autistic and is under 24/7 adult care. I just want to install Firefox, as he only looks at Lego videos on youtube. I've read that you can connect to a local account. Would that include my wifi provider?

I've already almost completed the process and now I'm scared to close things down. Is there a way to back out of the process? HELP! What do I do?

 

I don't run Windows 10 so all I can do is point you to sites that might help.

You can set up Windows 10 with a local account, not a MS account. See if this helps.
https://www.windowscentral.com/how-set-windows-10-local-account