Did you disable Xanga themes? That's the only way to access the old Look and Feel page, where you can paste those layout codes into the appropriate areas.
QUOTE
* 1. Disable Xanga themes (edit theme -> uncheck make this your active theme -> save)
* 2. Log into
xanga.com (look & feel) * 3. Copy (ctrl c) and paste (ctrl v) code to the specified fields