How To Make a Script Where You Click Once It Does Something, But When You Click The Second Time...?

I'd just be repeating other answers, but i'd like to explain why it works.

Toggling

We can create a variable with a boolean value, that changes the first time we click it, like this:

local Bool = true

local Button = script.Parent

Button.MouseButton1Click:connect(function()

    -- If bool is true, then...
    if Bool then

        -- This will be what happens on the first click
        print('Bool is true')

    else

        -- If bool is false, this is what will happen on the second click
        print('Bool is false')
    end

    -- We can use the "not" operation to convert the bool to it's opposite.
    Bool = not Bool
end)

Hope that made it a bit more clear, if not already.

EDIT: (in response to your counter question)

If we wanted to have different actions happen more than twice, we could use a number value as an increment, instead of a bool as a binary statement. Like this:

local Inc = 1

local Button = script.Parent

Button.MouseButton1Click:connect(function()

    -- If bool is equal to 1, then...
    if Bool == 1 then

        -- This will be what happens on the first click
        print('Bool is '..Inc)

    elseif Bool == 2 then

        -- If bool is 2, then ...
        print('Bool is '..Inc)

    elseif Bool == 3 then

        -- If bool is 3 then ...
        print('Bool is '..Inc)
    end

    -- Now, let's add 1 to "Inc".
    Inc = Inc + 1
end)

You could even make an array of events that we can index with the "Inc" variable. Like this:

local Button = script.Parent
local Inc = 1

local ButtonEvents = {
    function()
        print('Event 1')
    end,
    function()
        print('Event 2')
    end,
    function()
        print('Event 3')
    end
}

Button.MouseButton1Click:connect(function()

    -- If our index exists, then ...
    if ButtonEvents[Inc] then

        -- Call the value associated with the key (must be a function)
        ButtonEvents[Inc]()
    end

    -- Increase the increment
    Inc = Inc + 1
end)

Problem

I see your problem but you didn't really do anything besides ask so Il just give you a script

Solution

clicked = false
script.Parent.MouseButton1Click:connect(function()
if clicked == false then --1st click
clicked = true
end
if clicked == true then --2nd click

end
end)

clicked = false
script.Parent.MouseButton1Click:connect(function()
    if clicked == false then
        clicked = true 
        -- do stuff

    elseif clicked == true then
        clicked = false


        -- do stuff     

    end 
end)