Shop workers are just about the worst people for advice, so even if they'd been willing, their advice would probably have been rubbish anyway.
Cycling - the terms come from the nitrogen cycle.
Fish excrete ammonia. This is toxic to fish - it burns their skin and gills. In a 'cycled' tank there are bacteria which use this ammonia as food, but they take several weeks to multiply till there are enough of them to remove all the ammonia made by the fish and ammonia builds up and can kill the fish. The ammonia eating bacteria are present in tap water in miniscule amounts, but the ammonia feeds them so they multiply and very slowly they will start to eat the ammonia and turn it into nitrite. Unfortunately this is also toxic to fish - it binds to their blood and stops the blood carrying oxygen. There are more bacteria in the water that eat nitrite, again in miniscule amounts, and once the first bacteria start making nitrite, the nitrite eaters can start to multiply. The nitrite eaters turn nitrite into nitrate. This is not as toxic as the other two.
When fish are put into a brand new tank, we have to measure ammonia and nitrite at least once a day. At first you'll only see ammonia, and a few weeks later you'll start to see nitrite. Whenever you see a reading higher than zero for either or both, you must do a water change to get the reading back down to zero. It will take a few weeks before you have enough bacteria to keep both ammonia and nitrite at zero for you, so you will need to do a lot of water changes in the meantime.
Once the tank has grown enough bacteria they will remove all the ammonia made by your fish, and the nitrite made from that ammonia. When you get more fish, you'll have to grow more bacteria, so again, measure both ammonia and nitrite every day and do water changes to keep them at zero.
You need a test kit that measures both ammonia and nitrite. Liquid reagent ones are better than paper strip testers. Most of us use the API master kit which tests for pH, ammonia, nitrite and nitrate.
I haven't mentioned nitrate yet. The water changes to keep ammonia and nitrite low will also keep the nitrate level at the same amount as in your tap water. Once the tank is cycled - ammonia and nitrite staying at zero - you will need to do weekly 50% to remove the nitrate that is made.
Something you could do to help is get some live plants, particularly floating plants. Plants use ammonia as fertiliser, and take it up faster than bacteria. Floating plants are particularly good at this. If you can find some water sprite, buy it. This can be planted or left floating. I got mine off Ebay.
Another alternative would be to take the fish back to the shop and do a fishless cycle instead. This involves adding a solution of ammonia to the tank which feeds the bacteria until enough have grown, then you add fish. The method is written up on here in the How To Tips.
When the tank is ready for more fish, don't go by what the shop says. Ask on here instead. We will be able to guide you towards fish that are suitable for your tank and good tank mates for the fish you already have.
