|How is the downstream router connected to the upstream....wired or wirelessly?|
I suspect, since your downstream router is on a different subnet from the upstream router and you're plugged into the upstream network your problem at this moment is no route between subnets.
In order to configure a route between subnets you will need to plug directly into the downstream router, give yourself an IP in it's subnet. The you will be able to access the downstream router's configuration interface and add said route.
There are two different ways to connect a downstream router and unless you have a specific reason for separating the two onto different subnets it makes more sense to put them both on the same subnet for ease of communication between the two.
Before you do anything else I highly recommend you click on my name at the top of my response and read my "how-to" guide "add a second router to your LAN"
Whether you need the separation or not, it's worth the 5 minutes of your time it'll take to read that.