To change the useage Qt widget will change the buttons and tooblbars look on lubuntu in Qt applications. Check to apply Set GTk settings will apply to GTk applications. The checkbox to apply on single click has makes things you normally need two clicks for one click.
The icons theme changes desktop icons on your computer and if you click on the icon theme which is previewed on horizontal rows.
To launch appearnce in the menu -> prefrences -> Lxqt settings -> appearance. Another way is to press the Appearance button from LXQt configuration center or run lxqt-config-appearance from the command line.
