All content for Sven Co-op is located in the Sven Co-op\svencoop directory in the common Steam directory. When you open a ZIP file or package with maps, models, sounds, et cetera, you will put them here (although you can put them in svencoop_downloads but I’ll assume you’re running a server). Here are the file types and where to put them:
.wad – Texture package: place it in the svencoop directory.
.bsp – Map file: place it in svencoop/maps
.tga – Skybox package (should be multiple): place it in svencoop/gfx
.mdl – Model: place it in svencoop/models
.wav – Sound: place it in svencoop/sound
.spr – Sprite: place it in svencoop/sprites
.as – Script: place it in svencoop/scripts, although if it’s a map-based it should be in maps in addition to whatever instructions the mapper should give you.
There are Half-Life (Goldsource) plugins that might go in svencoop/addons but you’ll probably already know what’s going on if you have those downloaded.