Below you can see an image of the camp fire build part that has a convert component, Selecting the convert component will display the component settings for this blueprint.
Here you can set the items that the component uses for fuel in the Fuel Items array, in the image above you can see that wood is as a fuel item.
You can also set random item spawning in the Item Spawning Settings category shown in the image below.
In the image below you can set the number of inventory slot the convert component has, keep in mind that this is a total of the Fuel Slot, Convert Slots and Contains slots. So in the image below Inventory Slots is set to 11 thats 5 for Fuel Slots, 1 for Convert Slots and 5 for Contains slots.
In the image below some additional settings are highlighted. Require Fuel, if set to false then the convert component can convert items with no fuel items.
Drop Death Bag if true when the build part is destroyed it will drop a bag with its inventory contained items.
Storage Name is the name shown in the UI of the convert window in the HUD
Convert Type controls the type of cooking recipe the convert component uses. You set a cooking recipes convert type in the Cooking Recipes List.