I need help setting up Windows on a new PC

I've built and installed Windows on many PCs.  But, I've missed something fundamental.  I just bought one of those new mini PCs to use with my big-screen TV.  It came with Windows 11.  When I went through the setup process I wound up with the desktop I built for my brother.  I want to have a new installation with no connection or icons from a different install. What am I missing?  Please help.