Material Design skin

1. How to use it?
Just copy content of the Skins folder to X:\Program Files\RocketDock\Skins (where X is letter of disk where RocketDock was installed), run RocketDock, click right mouse button on your dock and choose Dock Settings... . Then select Style tab and select one of them from Theme list.

2. Where I should place content of Additional_icons folder?
Everywhere where you want. It's doesn't matter, because you can add folders with your own icons in Icon Settings... section.

3. How to make new icons look like the dark icons from Additional_icons folder?
    a) resize your existing icon to 186x186px,
    b) create new image with your graphics software in 256x256px resolution,
    c) just paste the content of your resized icon to new canvas/workspace,
    d) save as *.png and enjoy.

More Material Design icons you will find here:
materialdesignicons.com/

4. Indicator.
Turn off RocketDock and copy Indicator.png file from Indicator folder to X:\Program Files\RocketDock\Defaults\DefaultIndicator (where X is letter of disk where RocketDock was installed) - overwrite file, remember to backup default Indicator.png file.