Here I go.....
Open Cubase LE5. When Open Document Option screen comes up, select 'New Project>Empty'.
Set Project folder. Select location you want to save to (use the default for now, unless you have an external or secondary drive for audio). Create new folder for your project.
Setup driver for your interface: 'Devices>Device Setup...>VST Audio System'. Select US800 from ASIO dropdown menu. While there, check the 'Release Driver' box. It will allow you to go back and forth between Cubase and things like Media Player when either is open in background.
Set your connections from your interface to Cubase: 'Devices>VST Connections' (F4 gets you there quicker). Output default will be out 1&2. This is where your monitors should be hooked up to your interface.
---Click on 'Inputs' tab. Select 'Add Bus'>dropdown menu to 'Mono'>Ok. You can name your input bus here. Select the input channel you want to use on the US800 here, by left clicking on the yellow 'Device Port' section, that is to the right of the Input Bus you just created (Mic In 1 should be the default).
Create a track to record to: From main Project window, 'Project>Add Track>Audio>Mono>OK'.
--Now you have a mono track created to record to.
Many new to Cubase get lost here. The first section (window) on left side of screen, is called 'Inspector' window. Here you can control the Inputs, Outputs, record enable, monitor, Inserts, Sends, Fader, Pan, pre fader gain, and track delay, of
each individual track.
Most important in this window, is the Input/Output for the new track (and every subsequent track). The symbols look kinda like >] 'Input', and [> 'Output. This is where you route you buses created in VST Connections, to the track you want to record to. As well as where the 'Output' is directed. For now , Output should be to Stereo Out. By default, a mono track created, will use 'Mono In', after a mono bus has been created (as you already have).
Another note: If you happen to click on one of the tabs in the 'Inspector' window (Inserts, Sends, or Channel), you just click on the track name at the top of Inspector, to get back to the main Inspector window, to show Inputs/Outputs again.
Record to your track: Plug in your mic to input 1 of your interface (enable phantom power on back of unit if using a condenser mic). Enable record (target lookin thing in Inspector) AND click on the 'Monitor' button (icon that looks like a speaker).
--This allows you to hear what is coming into the Cubase track from your interface. After recording, click the 'Monitor' button off, to hear playback.
***Also, you can drag the edge of the window next to the Inspector window to the right, to display the most used Inspector functions.
***There are also changes you can make in 'File>Preferences' to make monitoring occur automatically (Tape Machine Style) when you hit record. Good for punching in. I can help further with stuff like that later.
Hope this helps man.