well first you have to have a modded xbox, do you have one? do you want to mod map pack maps so you can use them on xbl or do you want to mod old maps? to mod old maps you copy halo 2 to your xbox and ftp the maps you want to mod then you either mod them yourself or put in plugins then ftp the modded maps back to your xbox. if you want to mod map pack maps you need to download the map pack from xbl then find the maps you want to mod in your e drive and do the same thing you do with old maps.
ok softmods refer to the modification of your xbox console's software. halo mods refers to the modification of maps in halo. you need to do the softmod first here is a tutorial http://forums.afterdawn.com/thread_view.cfm/311710 or if you do not weant to do it yourself you can check out the link in my sig.
