Drag anywhere on the fire to orbit around it, and scroll to move closer or further away.
The names in the top right open and close the panels. The flame panel switches between the bonfire and the candle. The display panel sets the brightness, the flame size, the flicker, and how many embers and how much smoke rise from the fire.
Panels move: grab a header and drag. They stick to each other and to the edges of the screen, and a panel resting against an edge drops the rounded corners on that side. Grab any edge or corner to resize. Double-click a panel title to switch how the panels are laid out, between the movable layout and a single panel fixed in the top right.