The root folder is the main folder where the php files go.. also know as htdcos folder or www folder.
Go to phpmyadmin then go to your tracker database name end click on the stylesheets end you will see
1, 'ICGstation', 'ICGstation theme', 'default_phpbb_style'
etc... now to add the new theme
let's say the theme name is xmass so you add the folder xmass in the folder themes
now at stylesheetsclick on insert ,, at id put the next number 1,2,3 is busy now put 4
at uri put the exact name that you just put in folder themes so it is xmass then at name put the name ex: Xmass the click go.
All done, go to your tracker ..click the profile menu...scroll down to Stylesheets end select your theme end click submit.
Good luck