Hi Eminef.
Cycling is a common misconception and is usually misinformed by most lfs. The fact is most lfs are after your money and although I'm not directly accusing any lfs of deliberately giving wrong information but I will say thats its very good from the stores point of view if your fish die and you go spend more money on fish etc.
A filter new out of the box is just a piece of equipment and is not ready to deal with keeping fish healthy. In order for a filter to efficiently keep a tank healthy you need to first perform a cycle which allows beneficial bacteria to grow inside your filter which in turn can deal with the ammonia that your fish are constantly producing.
Personally I think you'd be best with a fishless cycle, if you've only got 2 fish in there at the moment then it would make sense to re-home them and use that opportunity to complete a fishless cycle with which time you can plan your stocking for when the cycle finishes. A fishless cycle is much easier for you and the fish. If you choose a fish-in cycle then large daily water changes are needed, usually as many as 2/3 changes a day in order to keep the levels of ammonia and nitrite in the tank down until the required bacteria have grown, therfore a fishless cycle is much less work for you and it also removes the risk of your fish getting poisoned. If you read the fishless cycle guide in my signature it will explain exactly what you need to do, you'd be best with the add and wait method.
Whichever cycling method you choose, you will need a good LIQUID test kit, dont get the paper test strips as they are highly innaccurate. A popular choice of test kit for many beginners is the API freshwater master kit which contains all the tests you will need for the cycle and is available in the UK online for about £18 which may sound alot but it has enough for 800 tests so will last 1/2 years. If you choose fishless cycle then you will also need some household ammonia which is available from boots.co.uk for about £2
Andy