The oven
Before you use the oven you should wipe it out with a damp cloth to remove any dust. When you first turn the oven on you will be able to smell residues from the oven surfaces being burnt off. It may be necessary to open a window for ventilation. The smell will disappear after using the oven a few times.
Heat zones
There are zones of heat within the oven. The temperature in the middle is the gas mark you have chosen. The top of the oven is slightly hotter and the lower shelf slightly cooler. The base of the oven is quite a lot cooler. You can make use of these heat zones when you are cooking foods requiring different temperatures all at the same time. You can use the base of the oven to warm plates. If you are cooking more than one tray of similar items, for example cakes or biscuits, swap the trays around during cooking. Or you could remove the top tray when the food is cooked and move the lower tray to the higher shelf to finish cooking.