If you 'start a new server' from the TF2 menu then you need to type
sv_cheats 1 in the console so you can type other console codes
bot will add a bot to the other team so you can go in game.
If it's a map you compiled then
bot will work.
If you start a dedicated server you have to have sv_cheats 1 set in a server.cfg file. (I still haven't got that to work, think the file needs to be with the map in steam/steam apps/2007 dedicated server/tf/maps)
Or have someone join game with you.
If only Valve could find a way to use more folders
