Are you going to hook up the second router to the first with a
cable?
Or do you hope to use the second router to connect wirelessly to the
first ?
In the first case, you are hanging an Access Point off of a router.
This should be fairly easy to do.
In the second case you are setting it up as a bridge. I don't know
your model, but most routers do not readily lend themselves to being
used as a bridge.