How do I add numbers to my simple scoreboard?

Basically, You can add Number to a Text because thats the rules.

If you want to then you can create a value of Number,

Example:

local Number = 0

(You can do it in ServerScript or LocalScript)

Just like then and you already created a Number inside of a Script.

To make the Text following the Number, you can do it with a script,

Example:

local Number = 0

while wait() do --Looping
    script.Parent.Text = Number
end

Solution:

local Number = 0

while wait() do --Looping
    script.Parent.Text = Number
end

local UIS = game:GetService("UserInputService")

UIS.InputBegan:Connect(function(input) 
    if input.KeyCode == Enum.KeyCode.E then 
        Number += 1 --Add a Value to Number
    end
end)

Notes for You:

1. (= +) is wrong, the correct one is (+=, No Space)

2. Write your script with Tools that this site give so we can understand it better

3. You cant add a Number to a Text

Hope It Helps!