No problem. Welcome to Linux and Ubuntu, by the way.
First, if you didn't install Steam from the Ubuntu Software Center, and didn't try, see if you can install it that way, removing Steam from your system beforehand. You may need to run
sudo apt-get update in a terminal beforehand (when it prompts you for your password, it's typing even if nothing shows up onscreen). I've also noticed that Steam only shows up in the Software Center when you click "show technical items" at the bottom.
If that doesn't help, see the Known Issues section on the Valve Developer wiki. Follow the instructions for Debian-based distributions:
sudo apt-get install lib32stdc++6
Let me know if these instructions don't make sense.