Above the bottom bar in Lightbow, you'll see a "Now Playing" bar which shows the currently-playing (or most recently played) preset, in this case "Rockstar". If you want to adjust the volume of the audio playing with that preset, you can do this using the icon at the right of the Now Playing bar. If you already see the volume icon, just press it, drag up and to the left, and you'll be able to set any volume you like. Alternatively, you can just tap that icon and Lightbow will keep that radial menu system up while you make multiple adjustments.
This is also the place to go if you want to switch to the Overall Brightness or Overall Saturation controls. To close the radial menu, just tap anywhere on the background outside the large circle, and Lightbow will keep the last-used control as an icon on the Now Playing bar.
Do you have any streaming hardware like the AirPort Express or anything that support AirPlay? You should see an icon right in the center of the screen, and if you tap it, you'll be able to select an audio output destination: