There are some database tutorials in the Tutorials section. The main things you need to do are:

• Install DBI and DBD::MySQL
• open a database handle:

      my $dbh = DBI->connect(...);
  [download]

• prepare the SQL statement:

      my $sth = $dbh->prepare_cached(...);
  [download]

• execute and finish the statement:

      $sth->execute;
      $sth->finish;
  [download]

There's nothing Perl-specific about this. Do you know SQL? Here's a tutorial.

You should also read the MySQL docs and the DBI docs.

Oh, and you'll need to get the data from the HTML form... but I assume you're using CGI.pm, so that's not an issue.