DB2 Session / user authentication

[eluser]Nial[/eluser]
I'm new to CodeIgniter, but am absolutely loving it so far! I've created a nice user registration script and am now looking to allow users to login. This is easy, but I'm confused with regards to session authentication. I found DB2 Session on the CodeIgniter wiki and liked the look of it, but have a few questions.

The first is: should I just place the code in my controller folder, and include it manually:

Code:

$db2session = new DB2_Session();

Or is there a special 'plugin' location that I should be slotting it into?

While I've found most of the CodeIgniter documentation to be excellent, DB2 Session's was a little sparse. I take it I'd call the sess_create() method when the user successfully logs in. And then instantiate DB2_Session in each of the controller constructors where it is necessary? To verify a users authenticity, I'd then use sess_read()?

Provided I've got the right idea: is this substantial, security wise?