I'll break it down, although I'm verbose, this is the simplest way.
Go to http://www.truecrypt.org/downloads
Scroll down to Linux and select the
Standard version that matches your bit depth (32-bit or 64-bit) and download it.
After the download completes, Double click on the downloaded file and it should automatically open with the Archive Manager.
At the top of the Archive Manager, click
Extract and select a destination folder, I picked
Start button on your keyboard (The button between the left Ctrl & Alt) and type the word
Terminal and press the enter key.
Here you will type commands inside terminal:
You'll need to Change Directory (CD) to where you extracted the truecrypt setup file, if you followed my example, it would be this (note your path is case sensitive):
To start the install, highlight and copy one of these commands and paste it into the Terminal window. (to paste, right click and select paste).
For 64 bit:
For 32 bit:
You then shuold get a xmessage window with an option at the bottom to
Install TrueCrypt, click it.
The next window will be an xmesssage License message, click
I accept and agree to be bound by the license terms
The next window will tell you how to uninstall it, if you don't plan on uninstalling it, you can skip this information.
The last window will be titled
TrueCrypt Setup and have the information where it installed and will finish with
Press Enter to exit... I recommend you press enter.
Start button again and type
TrueCrypt, (capitalization unimportant) and press enter to open
Tip: If you want it on your unit bar, simply use your mouse to drag the TrueCrypt icon to your unity bar.
Note: if you have an unconventional keyboard layout with no 'Start' you could open Terminal from the 'Dash Home' in the side-bar.