What directory to SSH transfer file to have Cydia install?

I am running jailbroken iOS 4.2.1. I have a .deb application file that is supposed to be a straightforward install. I am familiar with how to SSH files into and out of the iPhone file system. What directory to a copy this .deb application file to if I want cydia to install it? Or how else can I install it?

Thanks. That was very easy.