Preamble lyx 1.6 revtex4

[Scott, Robert]

I am attempting to use revtex 4 as a template to write a paper. The problem is 
that I need to alter some of the latex code in the 'preamble' but there seems 
to be no method for accessing this in later versions of Lyx. Earlier version 
refer to a menu called layout which allowed you to access this but aside from 
exporting to latex and then re-importing I cant see anyway of doing what I need 
to do. Any ideas?