[R-sig-ME] counseling for multilevel models

[Catarina Silva Castro]

Hello!
My name is Catarina and study in the Faculty of Sciences of the
University of Oporto, Portugal.
Within the framework of my master's thesis, I am using a set of data
on work accidents in a chain of stores.
The chain store is divided into different directions of operations and
each is associated monthly records of the number of registered work
accidents.
After several reviews, I think the multilevel models are the most
suitable but when implementing in R the models, I don't know how to
assign variables to different levels. When i use the function lme of
the nlme library or lmer of the lme4 library, all covariables that
include in the model are assigned to level 1 and do not know how to
assign them to higher levels.
I needed help to advise me on which the most appropriate functions
and libraries, if them are not, and I would to know how to assign
variables to different levels and get the best results for my study.
Waiting for reply. Thanks, Catarina