Download ServUO from the link at the top of the page, you can either download the current in development branch, or choose the release over on the right side, whichever is easiest for you.
Unzip this somewhere, this will be your server folder.
* At this point, I'd download and install and update the classic (2d) UO client. Make sure you know/remember where it is installed.
Go into your server folder, into the Config folder within, and poke through all those cfg files, changing what you would like. The most important ones are Server.cfg and DataPath.cfg, this is where you set your server name, and DataPath is where you specify where the client files are.
Now directly in your server folder, there should be a Compile.WIN - Release.bat running that should build (and for some weird reason launch) your server. If it does not, it may be that you need to install .NET (
.NET Downloads (Linux, macOS, and Windows)) the README on the ServUO github states you need .NET 5.0, so if it fails to compile/run, grab it from the download link above and install it, and you should be ready to rock.
On first launch it will ask you to create your owner account, I usually make this different from the account I play on. After that, the server should fully start. Log in with your new owner account, and I believe [createworld will spawn the default stuff for you.