Here's a sample script that will input data into a MySQL database using PHP:
$hostname = "localhost";
$db_name = "name of the database";
$db_user = "your database username";
$db_pass = "your database password";
$input_fname = "Dave";
$input_lname = "Clark";
$input_email = "email@example.com";
$query = "INSERT INTO name_table (firstname, lastname, email) VALUES ('$input_fname', '$input_lname', '$input_email')";
// Connect to database using variables already defined
mysql_connect($hostname, $db_user, $password);
// Input information in variables or stop script
$result = mysql_query($query) or die("MySQL Error");
That will put the values "Dave", "Clark", and "firstname.lastname@example.org" in the columns "firstname", "lastname", and "email". If the query fails, the die() function is called, which stops the script with an error message you specify. Obviously, you'll have to change the first four variables to fit your particular database, except for $hostname, which should be localhost in your case. If your database doesn't have a password, you can just omit that parameter from the mysql_connect() function call. Also, it's always smart to put these variables in a .php include file, for tighter security. Actually, because it seems you're hosting your own site, it would be even more logical to put the variables in a directory seperate from your web root, so that it can't be accessed at all outside of the script (and directly by you).
Note that this script assumes that MySQL is set up, that there is a database called "name of the database", and that there are three columns with appropriate names in that database. Setting up the database and tables can be done with another script, which I'll write for you if you want.
(sorry to widen the topic)