Is there an easier way for this script to turn on multiple lights?

Use for loop and table

Put all the lights inside a Folder or Model (I prefer folder) , which you can create on the explorer window, and put all the lights inside, just to keep things clean

local Lights = theFolder:GetChildren()
 -- This will put every reference to all objects inside the folder in a table
local isOn = Lights[0].LightPart.SpotLight.Enabled 
-- This will be used to determine wether the lights are on or off
local ClickHere = script.Parent.LightSwitch.ClickHere.ClickDetector
local SwitchA = script.Parent.LightSwitch.SwitchA
local SwitchB = script.Parent.LightSwitch.SwitchB

ClickHere.MouseClick:connect(function()
    if isOn then -- Check if its on
        isOn = false
        for _, v in pairs(Lights) do 
        -- Loops through the "Lights" table, if you are not sure how for loops works, go watch          YT videos on it, there are tons
            v.SpotLight.Enabled = false
            v.SpotLight.Material = Enum.Material.SmoothPlastic
        end
        SwitchA.Transparency = 1
        SwitchB.Transparency = 0
    else
        isOn = true
        for _, v in pairs(Lights) do 
            v.SpotLight.Enabled = true
            v.SpotLight.Material = Enum.Material.Neon
        end
        SwitchA.Transparency = 0
        SwitchB.Transparency = 1
    end
end)

Use an in pairs loop. This will loop through a table of whatever objects or values you provide. For example:

local playersTable = { -- table

    "Zyleak",
    "UristMcSparks",
    "Stickmasterluke"

}

game.Players.PlayerAdded:Connect(function(player)

    for i, v in pairs(playersTable) do
        if player.Name == v then
            player:Kick()
        end
    end

end)

You can place anything in a table. In this example, I was providing strings which would be used to identify players who I want to ban from my game because these are their usernames. Of course, it is much better to use their Roblox ids instead of their usernames but I just want this to be easier to understand.

On line 11, i means index. The position place of an object in the table is their index. The index of "Zyleak" is 1 because that is the first object in the table. The index of "UristMcSparks" is 2. Finally, the index of "Stickmasterluke" is 3. v, however, means value. The index shows where an object is in the table, but the value is self explanatory I guess. Value is value. It's whatever it is. Then, I told the loop to loop through the playersTable by placing it as a parameter in "pairs". After this line, you can do whatever you want to each value it loops through. I made it loop through the playersTable to check if the player's name was one of the string values I provided in the table. If it does match one of the string values, it will kick that player.

Now for your situation, loop through your table of lights as well. This is going to be more complicated though because of the names you gave each object. I will explain what I'm doing in comments.

 ClickHere.MouseClick:Connect(function() -- Function to turn on lights
    if Light.LightPart.SpotLight.Enabled == false then
    Light.LightPart.SpotLight.Enabled = true
    Light.LightPart.Material = Enum.Material.Neon
        for i, v in pairs(script.Parent:GetChildren()) do
        if v.Name ~= "Light" then -- making sure it's not Light because we already changed Light. I couldn't add Light in the loop because it doesn't have a number so this part would error
            local number = string.match(""..v.Name, "%d+") -- finds number in the light's name
            local childName = "LightPart"..number
            v[childName].SpotLight.Enabled = true
        v[childName].Material = Enum.Material.Neon
        end
    end
        LightSwitch.SwitchA.Transparency = 0
        LightSwitch.SwitchB.Transparency = 1

    else
        Light.LightPart.SpotLight.Enabled = false -- Function to turn off lights
        Light.LightPart.Material = Enum.Material.SmoothPlastic
        for i, v in pairs(script.Parent:GetChildren()) do
        if v.Name ~= "Light" then
            local number = string.match(""..v.Name, "%d+") -- finds number in the light's name
            local childName = "LightPart"..number
            v[childName].SpotLight.Enabled = false
        v[childName].Material = Enum.Material.SmoothPlastic
        end
    end
        LightSwitch.SwitchA.Transparency = 1 -- This is just for the switch animation.
        LightSwitch.SwitchB.Transparency = 0
    end
end)

Remember to capitalize the C in Connect, as just "connect" is deprecated. Feel free to fix this script if needed, and if you have any questions, I'll try to answer as soon as I can.