Before cooking anything inside a new electric fan-assisted oven, you should first remove any plastic tie-back/tags that hold the oven's metal racks and other equipment in place. When you have done that you need set the oven to a temperature of between 400 and 550 Celsius (between 204 and 288 Fahrenheit) for at least one hour in order to 'burn off' (get rid of) the new oily/chemical odours it emits from its insulation cavity (inner casing) bonding agents upon first use.
This extreme heat 'burning off' process emits such a powerful, vulgar, oily/chemical odour (that can be harmful and nauseous) that it will smell out your whole house. Hence one reason why you should ALWAYS open your kitchen window(s) and door(s) and stay out of the kitchen until the 'burning off' process has completed.
You may have to perform this 'burning off' process for one or two hours longer until the vulgar smell is no longer being emitted. A maximum of three hours should be sufficient. After that, allow the oven to completely cool down before cleaning its inside walls and metal racks with standard cleaning materials.
If you forget to perform the 'burning off' process and just cook something inside your new electric fan-assisted oven straight away, DO NOT eat any food that was cooked inside your new fan-assisted oven during this particular 'burning off' (very high temperature) process unless you want a potential 'stomach upset' or more serious sickness.
When baking something inside a new (now 'burnt off') fan-assisted electric oven, especially as an absolute beginner to using one, you will more than likely find yourself experimenting with its temperature settings in terms of baking and deciding when to use the fan-assisted electric oven purely as an electric oven (without the fan). This experimentation process is quite normal simply because the temperatures of a modern day fan-assisted electric oven versus a traditional gas cooker differ slightly.
As a general rule, you should take at least 20 degrees celsius off a bread recipe for example when following its traditional electric or gas oven temperature. So if the bread recipe states 200 degrees celsius in a traditional electric or gas oven for example, try using a temperature of 180 degrees celsius (or slightly lower) on a new fan-assisted electric oven (fan oven).
When I bake bread inside a fan-assisted oven (with the fan on), I always set its temperature to 150 degrees celsius (170 celsius on a traditional electric oven, gas mark 3). I found it bakes the bread perfectly after a minimum of 30 minutes, and a maximum of 40 minutes, whereby a temperature of 180 degrees celsius for example tended to be a disaster (burnt top with a raw inside). So the rule tends to be 'bake slightly longer at a lower temperature'.
As part of the pre-baking process you should always preheat your fan oven for 30-60 minutes, prior to baking bread or a cake for example, so the bread dough or cake mixture is not starting in a cold oven. You should know, through your pre-baking experiments using different temperatures, the exact temperature to preheat your fan oven.
I always preheat the fan oven at 140 degrees celsius while creating a cake mixture for example. That way the fan oven is hot enough by the time I have measured the ingredients, created a mixture from them and put the mixture inside a baking tin; and into the now 'hot enough' fan oven.
With a fan oven it should not really matter which shelf you put the baking tin (cake mixture) on, but as a rule I put it on the middle shelf; even though the hot air is being blown equally around the fan oven. If you are getting a too-burnt bread or cake top, even with a suggested baking tin size, you might want to try a slightly wider baking tin.