How do you assign a saving variable to a player? [UNANSWERED]

Ok. So, I understand this as a very basic idea of assigning a variable, but I want to be able to have the ability to update and save. I've read up on the DataStoreService and I am just confused on how I do this in reality for my script. I just want to be able to store a numerical value.

So far, I have basically this. I need help assigning the value to the actual player. Im not sure how to effectively assign the number to the particular player when they touch the block.

local game = game:GetService("DataStoreService"):GetDataStore("StageNumber")
 local key = "user_" .. player.userId 

function PlayerAdded ()
 game.Players.PlayerAdded:connect(function(player)
    player = workspace:FindFirstChild("Player")
    if (game:GetAsync(key) >= 1)
     then print ("Welcome Back " .. player.GetFullName())
    else game:SetAsync(key, 1)
        print ("Welcome " .. player.GetFullName())
    end
end)
end
for _, player in pairs(game.Players:GetPlayers()) do
    PlayerAdded(player) -- Use your player added handling function here.
end

if (game.Players:FindFirstChild("Player1") == true) then
    game:GetService("DataStoreService"):GetDataStore("StageNumber"):SetAsync("Player1", 1)
end

Please help me understand this.

Thanks for your time, -rider