Tallima: NWN has a few different things. Whatever you download, follow the instructions.

Portraits go into /portraits
Overrides go into /override
Haks go into /hak

Good luck!

Jason_the_Iguana: Well, to elaborate a bit:

Firstly, unlike mods in other games, mods in Neverwinter Nights are mostly standalone adventures, or "modules," called "mods" for short. It's confusing. "Extra companions" and such aren't really a thing. There is plenty of custom content that changes the base game, adding more creatures, or changing spells, or different environments or custom music, but those are typically bundled with those standalone adventures.

You CAN add some kinds of custom content to the base game, but they're typically called "overrides" rather than "mods." Because you put the stuff in your Override directory. But since there's no such thing as mod-managers, this should be done with care.

For example: I use the Alternate Combat Animations Pack as an override, letting my characters select different fighting styles. But unless I'm playing a module that integrates this pack, my character is the only one that uses it. All NPCs fight in the normal style.

So, if you want to change things up, I recommend you find some custom adventures to play. This post on the vault forums has huge themed lists in all kinds of categories. There are also various recommendation threads on this forum. Should be easy to dig up. You can also find modules on some other sites, such as Nexus, but all but a few can be found on the vault.

Anyway, installing them is typically pretty easy. There are a bunch of files to download at the bottom of each modules page. Sometimes they're bundled in an archive. You download these files, open the directory you installed the game in, and then put the files in the appropriate sub-directory.

.mod files go in "[game dir]\modules"
.hak files (custom content) go in "[game dir]\hak"
.bmu files (music) go in "[game dir]\music"
.tlk files (in-game text changes) go in "[game dir]\tlk"
.mov files (movies) go in "[game dir]\movies"

Very occasionally something is supposed to go in the override directory. I don't like modules that do that.

Portraits, which come as a set of 4 or so .tga files, go in the "[game dir]\portraits" directory, but they're only used for characters you make, so you can download them separately or make your own. If modules have custom portraits for NPCs, they're just bundled in with the HAK files.

That's everything I can think of. If you have more questions, ask away, but it's really not very hard. Just check the readme files of the stuff you download if you're unsure.

Hickory: Galaxy, not gog... G.A.L.A.X.Y. Right, now that's out of the way, Galaxy does not support mods. Go to the Nexus, find a mod that you want or like and read the instructions.

BlackfoxKitsune: I would kindly ask you to go and find a Potato to go Troll.

Hickory: Another clueless twit.

PeterScott: You certainly are doing your best to act like one.

Hickory: Another clueless twit.

BlackfoxKitsune: I'm the OP of this thread

Hickory: Oh, you're SO special. How could I be so careless!?

Idiot.

passionata: A Neverwinter Fan looking for mods is way better off visiting: http://neverwintervault.org/ the spiritual successor of nwvault on IGN!