Cycling a tank in simple terms means having a mature water environment for your fish. There are several ways fishkeepers do it. It is a job that needs patience whichever method you choose.
Raw water, which is plain tap water is harmful to fish. Even once you've put in additives. So what you need to do is let nature give you a helping hand. Generally cycling a tank takes the minimum of 3 weeks before you add fish. Now if like many newbies you can't bear to see an empty tank, you can add 2 or three small hardy fish into the water after a week or so. No more than that. After another couple of weeks, you could add another couple of other small to medium fish and gradually build up that way in fortnightly cycles. All this time during the cycling process the tank must be fully functional as though it were running properly even when you have no fish in it. The only thing you don't need to do for the first month or so is change the filter. Food must be fed sparingly. No food must be allowed to settle at the bottom of the tank, this will pollute the water and cause you problems. Whenyou have only 3 fish in the tank, feeding once a day is sufficient, a small pinch.
I hope this has helped.