The position of the tray depends on the food you are baking. Generally, when baking cakes or bread, the recipe (that is, the recipe) will have specific instructions, so that you can put it on the upper level and put it on the lower level. Preheating is also stipulated, as long as it is done according to the requirements of the prescription. Generally, the preheating time is 10 minute, with some differences. See the prescription for details.

Preheating operation: adjust the temperature to 220 degrees (or the degree required by the prescription), then adjust the firepower (such as ignition, ignition according to the prescription), and finally select the time 10 minute. After 10 minutes, the oven is preheated and you can put in what you want to bake.

If you don't understand anything, you can go to Sina food blog to see and learn. Recommend a food blogger "Junzhi" to read his blog. I will do what I want in strict accordance with his recipes, and I will definitely make cakes and bread. I have been using his formula to make it, and the success rate is very high.