Most likely you'll set Tools > USB Type to Disk(SD Card) + Keyboard. That makes the SD card available to the PC as a USB mass storage device. You'll probably use Keyboard.print() to send commands to the computer to cause it to use files stored on the SD card.
Teensyduino also has a USB Type called Disk(internal) + Keyboard. It works the same way, but uses the tiny amount of extra flash memory as the disk media. On Teensy 2.0, the flash is read-only. Teensyduino pre-loads the flash with your files. If you haven't provided any files, the disk is initialized with a readme file that gives you specific instructions. The readme is generated with pathnames specific to your PC, so please read that file for help.
Like any large project, the best approach is to break it into many smaller, easily manageable projects. You've already made the LED blink, so you're on the right path. This may be obvious, but to move forward, try making progress on these individual items.
1: Use the Keyboard.print() to send a command to your PC
2: Populate the internal disk with a tiny file.
3: Find a command that can access the disk.
4: Connect a LCD and use lcd.print() to make it display text
5: Connect the SD adaptor and use Disk(SD Card) instead of Disk(internal)
On item #1, you might take a look at Irongeek's website.
http://www.irongeek.com/ He's published lots of examples of keyboard commands to do stuff. I believe he even wrote an Arduino library to automate some of the work. I haven't personally used it, so the best help I can give is directing you to his site.
Then again, you might find simply using Keyboard.print() is effective enough. Usually for student projects, the deadline is absolute, but partial success with a good explanation of how you might achieve the rest often passes. So I'd try doing those steps ASAP, so if time runs out, you'll at least have some stuff working that you can present.