How would I go about with a narrator for my game?

Since it sounds like you are going to use audio recordings, I'll show you that way.

First, you could try to run a loop to see how far the player is away from something.

local played = false

while true do
    wait()
    if played == false then
        local dist = player:DistanceFromCharacter(game.Workspace.Part.Position) --Replace player with however you can access the player. Replace game.Workspace.Part to the path of a part within the area where you want the sound to play or a vector3.
        if dist <= 10 then --replace 10 to the distance you want between the player and the part until the sound is played
            played = true
            game.Workspace.sound:Play() --Replace to path to sound.
        end
    else
        break
    end
end

Second, you could try to make it trigger when you touch an object, such as a door.

local touched = false

game.Workspace.Part.Touched:Connect(function(plrpart)
    if touched == false then
        if plrpart.Parent:FindFirstChild("Humanoid") then
            touched = true
            local plr = game.Players:GetPlayerFromCharacter(plrpart.Parent) --this is just if you want to be able to access the player.
            game.Workspace.sound:Play() --Replace to path to sound.
        end
    end
end)

Third you could do it when something is clicked, assuming you have a click detector.

local clickdet = game.Workspace.Part.ClickDetector --Replace to path to click detector
local clicked = false

clickdet.MouseClick:Connect(function(plr)
    --plr is to access the player who clicked if you need to
    if clicked == false then
        clicked = true
        game.Workspace.sound:Play() --Replace to path to sound
    end
end)

This all assuming your game is single player, since Stanley Parable is single player. (at least I think so) If not, a few changes will have to be made to the scripts so they can run again but not by the same player and can only be heard by one player. (unless you plan on all the players triggering the stuff together) That is when the whole entire narrator system would have to be run from a localscript I believe. (along with making sure the players triggering it are your localplayer)

Hope this helped.