You will need to copy the following files from your currently-installed
Ultima Online (or your CD-ROM) to the ${PREFIX}/uox3 directory.

map0.mul
staidx0.mul
statics0.mul
verdata.mul
tiledata.mul
multi.mul
multi.idx

Also, edit ${PREFIX}/uox3/uox3.ini to set your world's name, IP address,
and other configuration data.

To allow clients to play on your shard, have them edit their "LOGIN.CFG"
file (in their UO directory).  It should contain one line which reads:

LoginServer=Your.Shards.IP.Address,2593

The server is created with three default accounts.  They are:
- username "username", password "password"
- username "guest1", password "pass1"
- username "guest2", password "pass2"

You will probably want to change these.  In particular, the very first
account in the file is "special" because it has full Game Master (GM)
privileges!  The file to edit is called accounts.adm, and is located in
${PREFIX}/uox3.

Documentation on the server and the various commands available to Game
Masters (GM's) and other higher-level characters is available in the
directory ${PREFIX}/uox3/docs.

You may be interested in the Chaos GM Tool (CGMT).  This is an excellent
(Windows-based) tool that makes being a GM or Counselor extremely easy.
Create objects, vendors, monster spawns, answer players' help calls, and
much more, using a simple point-and-click interface.  No more memorizing
complex commands!  For more info on CGMT, or to download a (free) copy,
visit the CGMT web site at: http://www.prodes.org/cgmt/.

Have fun!