In the edit menu you will have all the options to style your fire
There is no need to know CSS to style your fire, as the fire editor already has many design options.
On this screen you will find the fire_id, which is important if you want to manipulate it via javascript later. Use the controls to change text size, upload images, change the background, add sound effects and much more. At the top of the screen there will be a tab to add the actions of the fires.