This is essentialy what you want, put it in a local script in starter player scripts.
local uis = game:GetService("UserInputService")
local mouse = game.Players.LocalPlayer:GetMouse()
uis.InputBegan:Connect(function(input, gp)
if gp then return end
if input.KeyCode == Enum.KeyCode.E then
if mouse.Target == [YOUR TARGET] then
-- your code here
end
end
end)