Two Linksys WRT54G routers

My primary router is a WRT54G. It serves two computers in our home wired and this end of the house wireless.

I have a Cat5 wire from the router going under the house to the other end of the house.

It is plugged into the input of a second WRT54G which I just got. It was bought to provide a strong signal to that
end of the house.

Some has said I need to configure it to be a repeater.

Any help is appreciated.

additional information that may be pertinent:

the original Primary router is version 3.1

the secondary router I was interested in using as a repeater or extender is version 5