This download looks like an addon. You need to extract the downloaded zip and put the addon folder in your Garry's Mod addons folder. You should end up with a directory structure similar to below:
-
steamapps
-
common
-
garrysmod
-
garrysmod
-
addons
-
DPFilms Gordon Freeman <-- Addon folder!
-
e.g.
-
lua
-
maps
-
materials
-
models
-
etc
- DPFilms Gordon Freeman/
- info.txt
- lua/
- autorun/
- Anticitizen_one.lua
- Anticitizen_one_Player.lua
- materials/
- models/
- DPFilms/
- Characters/
- Kran4es_Freeman/
- cs_office.vtf
- eyeball.vtf
- eyeball_l.vmt
- eyeball_r.vmt
- eye_ao.vtf
- facemap_sheet.vtf
- facemap_sheet_ep2.vtf
- facemap_sheet_ep2_n.vtf
- facemap_sheet_n.vtf
- frame_mat.vtf
- frame_mat_n.vtf
- glassesframe_front.vmt
- glassesframe_side.vmt
- glasslens.vmt
- glasslens_ep2.vmt
- glass_mat.vtf
- glass_mat_ep2.vtf
- gordon_headmap.vmt
- gordon_headmap_ep2.vmt
- hairbits.vmt
- hairbits.vtf
- hairbits_ep2.vmt
- HEVhelmet_exp.vtf
- HEVhelmet_glass.vmt
- HEVhelmet_sheet.vmt
- HEVhelmet_sheet.vtf
- HEVhelmet_sheet_ep2.vmt
- HEVhelmet_sheet_ep2.vtf
- HEVhelmet_sheet_ep2_n.vtf
- HEVhelmet_sheet_n.vtf
- HEVsuit_sheet.vmt
- HEVsuit_sheet.vtf
- HEVsuit_sheet_ep2.vmt
- HEVsuit_sheet_ep2.vtf
- HEVsuit_sheet_ep2_n.vtf
- HEVsuit_sheet_exp.vtf
- HEVsuit_sheet_n.vtf
- mouth.vmt
- mouth.vtf
- mouth_n.vtf
- VGUI/
- entities/
- Anticitizen_one.vmt
- Anticitizen_one.vtf
- models/
- DPFilms/
- Props/
- gordon_glasses.dx80.vtx
- gordon_glasses.dx90.vtx
- gordon_glasses.mdl
- gordon_glasses.phy
- gordon_glasses.sw.vtx
- gordon_glasses.vvd
- HEV_helmet.dx80.vtx
- HEV_helmet.dx90.vtx
- hev_helmet.mdl
- HEV_helmet.phy
- HEV_helmet.sw.vtx
- hev_helmet.vvd
- Inaki/
- Characters/
- gordon_freeman.dx80.vtx
- gordon_freeman.dx90.vtx
- gordon_freeman.mdl
- gordon_freeman.phy
- gordon_freeman.sw.vtx
- gordon_freeman.vvd
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