How do I go about doing this? How do I store username and passwords so they are associated with eachother and can be retrieved when the user logs in again?

There are many, many ways of doing this. First off when I did a simple search of the PM site I got this discussion, this discussion and that discussion for starters.

As far as where to store user tokens you can do any of the following with varying degress of utility:

1. Flat files
   • .htaccess and use Basic Auth
   • Your own version of a password file
   • Many other variations of a theme...
   • Hard-coded in your Perl code (danger Will Robinson!)
   • In a database

Last thought (for now) is that using HTTPS vs. HTTP is a factor of how sensitive your data is, how paranoid you are and in some cases your pocketbook. HTTPS will encrypt the communication between your browser and the server and HTTP will not.