Run/Walk Button

Where to put it?

StarterGUI

ScreenGUI

TextButton

LocalScript

Run Code

local button = script.Parent

button.MouseButton1Click:Connect(function()
  local player = game.Players.LocalPlayer
 player.Character.Humanoid.WalkSpeed = 50
 
end)

Walk Code

local button = script.Parent

button.MouseButton1Click:Connect(function()
  local player = game.Players.LocalPlayer
 player.Character.Humanoid.WalkSpeed = 16
 
end)