Onclicked? script? help? needed

I need help on my new script. The help i need is that i want it so that the person presses a button using gui's and then the shirt and pants appear on the human.

--Made by codboy22


local shirtTemplate = "http://www.roblox.com/asset/?id=59323775" 

local pantsTemplate = "http://www.roblox.com/asset/?id=59404936" 

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local faceID = "" 



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local delete_Tshirts = true     

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-- Main coding:

function changeClothing(p)

    if (p.Character) then 
        local shirt = true 
        local pants = true 
        local face = true 
        if (shirtTemplate == "") then shirt = false end 
        if (pantsTemplate == "") then pants = false end 
        if (faceID == "") then face = false end 
        local S = Instance.new("Shirt") 
        S.Name = "Shirt" 
        S.ShirtTemplate = shirtTemplate 
        local P = Instance.new("Pants") 
        P.Name = "Pants" 
        P.PantsTemplate = pantsTemplate 
        for _,v in pairs(p.Character:GetChildren()) do 
            if (v.className == "Shirt") then 
                if (shirt) then 
                    v:remove() 
                end 
            elseif (v.className == "Pants") then 
                if (pants) then 
                    v:remove() 
                end 
            elseif ((v.className == "Part") and (v.Name == "Torso")) then 
                if ((delete_Tshirts) and (v:findFirstChild("roblox"))) then 
                    v.roblox:remove() 
                end 
            elseif ((v.className == "Part") and (v.Name == "Head")) then 
                if ((face) and (v:findFirstChild("face"))) then 
                    v.face.Texture = faceID 
                end 
            end 
            if (shirt) then 
                S.Parent = p.Character 
            end 
            if (pants) then 
                P.Parent = p.Character 
            end 
        end 
        print("Changed " .. p.Name .. "'s clothing") 
    else 
        print(p.Name .. "'s character was not found; function returned") 
        return 
    end 
end 

game.Players.PlayerAdded:connect(function(p) 
    repeat wait() until p.Character     -- Wait for the new player to spawn 
    changeClothing(p) 
    p.Changed:connect(function(x) 
        if (x == "Character") then 
            game:service("RunService").Stepped:wait() 
            if not (p.Character) then return end 
            changeClothing(p) 
        end 
    end) 
end) 
script.Parent.MouseButton1Down:connect(onClicked)