The obvious answer is that this is such a simple task, that if it is stumping you you should not be doing it. The second assumption is that you have the the normal thing and it is still leaking. If that is the case, then the copper tubing could be damaged. That is something that cannot be evaluated from here. But to answer the original question. Assuming you mean the pipe from the wall, you slide the compression fitting on to the tubing and tighten the compression nut firmly. Turn the water on and if it drips, tighten it a little more. If the drip does not stop or becomes stream, stop and call a plumber since the tubing or fitting is bad and you are now past your point of incompetence and should not do anything else.