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
          • Huge e2 pack <-- Addon folder!
            • e.g.
            • lua
            • maps
            • materials
            • models
            • etc

• Huge e2 pack/
  • (e2)spy_troll.txt
  • _autosave_.txt
  • _shutdown_.txt
  • 10_prop_limit_game_e2.txt
  • 3d_holo_anim_checker.txt
  • 3d_holo_multi_clipping_demo.txt
  • aimer Test e2.txt
  • air_plane.txt
  • Amazon.txt
  • anything_chip.txt
  • applyforce_pet.txt
  • applyforce_ragdolls.txt
  • array_testing_chip.txt
  • arrays_with_holos.txt
  • attack!.txt
  • Awesome_Faces_by_Spoon_God.txt
  • backup.txt
  • ball.txt
  • ball_companion.txt
  • balls of steel.txt
  • balls_of_penis.txt
  • ballz.txt
  • ban_hammer2.txt
  • BAN_SLAP.txt
  • basketball.txt
  • big_ones.txt
  • bird.txt
  • bitch_slap.txt
  • bloody_vegina.txt
  • bored_e2.txt
  • box_car.txt
  • captians_music_player.txt
  • car turning.txt
  • Car_Battery.txt
  • car_control_diehard.txt
  • car_e2.txt
  • car_hydraulic_controller.txt
  • car_radio.txt
  • car_system.txt
  • Castle Hat.txt
  • chip 2.txt
  • clown_hat2.txt
  • colour.txt
  • colourchanger.txt
  • colourchanger_adv.txt
  • computer.txt
  • computer_fan.txt
  • console_screen_test.txt
  • conssole_screen_made_by_kevin.txt
  • CrowbarHax.txt
  • cube invasion.txt
  • cube.txt
  • darkminds_factory.txt
  • diehards,_eyeball.txt
  • diehard's_holo-controle.txt
  • diehards_plane.txt
  • digital_screen_test.txt
  • drone 2.txt
  • e2 holo boat racers.txt
  • e2 holo single boat.txt
  • e2 keypad.txt
  • e2missle5.txt
  • edit_me!.txt
  • egp_draw.txt
  • egp_test_chip.txt
  • elevator_e2.txt
  • epic_turret.txt
  • Evil E2.txt
  • example.txt
  • explosive_turret.txt
  • eye_angle_gun.txt
  • eye_ballllls.txt
  • fairy.txt
  • fairy_v1.txt
  • fighter_jet.txt
  • filename.txt
  • firenmahlazor.txt
  • Follower_v7.txt
  • following_guy.txt
  • for_fags.txt
  • for_loop_creating_holos.txt
  • fore_minges.txt
  • forest.txt
  • GM_flatgrass model.txt
  • gun_for_anything.txt
  • Halloween.txt
  • hitler.txt
  • holo.txt
  • holo_building_test.txt
  • holo_character.txt
  • holo_character_remake.txt
  • holo_character_that_moves.txt
  • holo_collision_test.txt
  • holo_head.txt
  • holo_jet_above_head.txt
  • holo_lavalamp.txt
  • holo_life.txt
  • holo_spotlight.txt
  • holo_test.txt
  • holo_test_chip.txt
  • holocolorchangertest.txt
  • hologram.txt
  • holograph.txt
  • holohat.txt
  • holoposwithtimer.txt
  • holorocket.txt
  • holoshapetest.txt
  • holo-ufo.txt
  • holo-whip.txt
  • hopper.txt
  • How to Use.txt
  • human.txt
  • iscooter_system.txt
  • jet.txt
  • jetpack_(made_by_[jg]_someone920).txt
  • joy_stick.txt
  • Jurkey holo.txt
  • keypad.txt
  • keypad_hacker.txt
  • killer.txt
  • kills_all_players.txt
  • level 1 sentry e2.txt
  • lights.txt
  • Maddy's NPC Programmer.txt
  • makes_all_players_blind.txt
  • memory.txt
  • minge_holo.txt
  • mini_boat.txt
  • minimap.txt
  • monowheel.txt
  • movement.txt
  • movingcoloring_test.txt
  • ninja_style.txt
  • no noclip =).txt
  • plane_system.txt
  • plankton.txt
  • pokemon_ball_made.txt
  • portalgun e2.txt
  • pos_test.txt
  • prop_test.txt
  • Ragdolls to Zombies.txt
  • rainbow!.txt
  • ranger_test.txt
  • ranger_test2.txt
  • rave.txt
  • rocket_launcher.txt
  • sb_ship_controll.txt
  • sb_turret.txt
  • sims_plumbob_health_indicator.txt
  • skin_changer_(camo).txt
  • skin_changer_(money).txt
  • skin_changer_(stripes).txt
  • skin_changer_(warpsheet).txt
  • sky_walker.txt
  • smoke_trail.txt
  • snake e2.txt
  • snow_man.txt
  • snow_man_plmodel.txt
  • snowman.txt
  • soundplay_test.txt
  • Southpark kenny.txt
  • spy_bot_system.txt
  • stabalization_chip.txt
  • stickman2.txt
  • suit ne weps.txt
  • super_tele_power.txt
  • suspension_holos.txt
  • tank_control_by_darkmind.txt
  • targeting_system.txt
  • test.txt
  • test_car_system.txt
  • test_chip.txt
  • test_delete_after.txt
  • test_holocreating.txt
  • test_train_control.txt
  • text.txt
  • time_bomb.txt
  • tornado_vortex.txt
  • tracker.txt
  • Trail holo.txt
  • trap 2.txt
  • triangle.txt
  • turrent_test.txt
  • turret.txt
  • turret_controlle.txt
  • turret_controller_by_diehard.txt
  • visible.txt
  • vtol_control.txt
  • vtol_controller.txt
  • vtol_system.txt
  • weapon.txt
  • whack_a_mole.txt
  • what_whats_this!!.txt
  • wheel_position_test.txt
  • wheels_for_car.txt
  • Whip e2.txt
  • xmas_hat.txt
  • xmas_tree.txt
• README.txt
• gm_big_flat_water0002.jpg
• Gimme shelter.mp3

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