Server to Client

Scripts

ServerScriptService

local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local remoteEvent = ReplicatedStorage:WaitForChild("RemoteEvent")
 
local function onPlayerAdded(player)
  remoteEvent:FireClient(player, player.Name)
end

Players.PlayerAdded:Connect(onPlayerAdded)

LocalScript under TextLabel

local label = script.Parent

local ReplicatedStorage = game:GetService("ReplicatedStorage")

local remoteEvent = ReplicatedStorage:WaitForChild("RemoteEvent")

local function onNotifyPlayer(name)
    label.Text = 'Welcome ' .. name
    wait(5)
    label.Visible = false
end
 
remoteEvent.OnClientEvent:Connect(onNotifyPlayer)