How do you create a mouse clicking function on local script on roblox studio?

I wana to know so i can make a game

If you are talking about when a player clicks on a gui, then

local Button = script.Parent
Button.MouseButton1Click:Connect(Function()
--Your Code Here
end

Make sure to put this script in a textbutton or an imagebutton

If you want to just check if the player makes a mouse click in general, then this code will be right for you.

-- This should be in a local script
local plr = game.Players.LocalPlayer
local mouse = plr:GetMouse()
mouse.Button1Down:connect(function()
-- When you press the button
end)
mouse.Button1Up:connect(function()
-- When you let go of the button
end)