someone please help me with starting a multiplay game...

This is a shot in the dark but in your UnrealTournament\maps folder try making a copy of cityintro.unr and renaming the copy DM-Cityintro.unr. Or. you could download the file from Nalicity (do a search to find the URL) but since you have played it before it suggests you have the map already. Sorry if it doesn't work.

Go to you cache folder in the UT directory and open the cache.ini file and you'll see a long strings of numbers followed by the real names of the files. Now find the file with that long string of numbers that matches to the ini and rename it to the name that the cache file said.

it might be something like this..

in the cache ini-54893124585633213DM-Map.unr
rename it to just the DM-Map.unr

Then move it to you maps folder... Keep in mind there might be some texture files that need the same treatment. Your better off getting the map through Nali or one of the others

Or you can get a utility that extracts and installs them from you cache

http://www.planetunreal.com/modsquad/others/utmap.htm

Once you've gone through the other suggestions, and if you're still having trouble starting or configuring a multiplayer server, check out The Admin Page.

Lots of nice howto's, guides and utilities for server admins.