1.first make a folder called usermaps in cod4 directory.

2.make another folder in it called mp_mapname example mp_canal_bf3

3.copy the .ff files in it like mp_canal_bf3.ff and mp_canal_bf3_load.ff

4.copy the .ff files also in zone/english/

5.then copy the .iwd file in the cod4/main/ and rename it into iw_?.iwd file example from mp_canal_bf3.iwd to iw_14.iwd

6.optional:if you want to play custom maps with mods then inside cod4/mod/ make a folder [like mp_canal_bf3] and copy the .iwd file inside it

7.to run it simple start a server with any map.

8.after the server starts in the console write /map mp_mapname like /map mp_canal_bf3

9.you are done the map will run.Enjoy