Here is some of the info:
Creating an Offline account, if you plan to have a LAN game without internet access.
1) Manage accounts
2) Create Account ==> Accept Terms
3) [Single Player Tab]
4) Player name ==> Create Account
Now when you start BF2 without internet access, it may take several minutes before the Player ID screen comes up. When it does, click the single player ID to play offline.
Creating LAN game with BOTs:
1) Get the Host to start a local LAN game. Map doesn't matter at this point.
2) Get the other computer(s) to go to join LAN IP address of the Host and click but NOT JOIN the server.
3) Have the Host server quit and start a single player map of choice.
4) Have all people then click JOIN for the server and viola, LAN with bots
There are ways to play the larger maps, unlock all the weapons, and to increase the # of BOTs for single player games. Just have to edit some files.