Upload files from upload folder to your xenforo root.
Then install the addon like you would install any other addon in zenforo.
These next instruction is important for custom skins make sure you put folder in each of your custom style folders.
For example for BP skins you would put it here. BP-Black>CollapsibleSidebar.
Repeat for each of your custom styles.
This feature is similar to Vbulletin hide and unhide sidebar feature for the xenforo forums.