Open Devices > Device Setup, in the Remote Device, find your Fader Port. If there is no one, click to the “+” button, and insert new Fader Port Remote Device. Then click on it, and on the right side, set MIDI Input, and MIDI Output. These will be named like “USB PreSonus Fader Port”, or something, like this.
I recommend to update Fader Port firmware from the PreSonus web page. If you are on Windows, you are lucky. If you are on Mac, you have to update the firmware from Mac OS X 10.5 (or lower), or you have to do this on different Windows-based computer.
Fader Port sucks! If you are using Cubase only, Steinberg CMC DAW controllers work much more better, in my opinion. And Fader Port is very noisy! Virtual faders of CMC has no noise – I love this!