Help for a leaderboard datastore ?

Hi ! i need help with my leaderboard, is work but when i leave the server the Time Played return to 0.. i want save my progression with datastore but i don't know how it's work ? Thanks for help :)

function onPlayerEntered(Player)

    local stats = Instance.new("IntValue")
    stats.Name = "leaderstats"

    local secs = Instance.new("IntValue")
    secs.Name = "Time Played"
    secs.Value = 0


    secs.Parent = stats

    stats.Parent = Player

    while true do
        secs.Value = secs.Value + 1
        wait(1)
    end
end

game.Players.ChildAdded:connect(onPlayerEntered)