I think it can be good to read a bit more about it. Check here.
Anyway, you need to say the name of the file to post to: <input type="submit" action="file.php" name="Submit" />
for example.
And you need to have more inputs than the submit.
Acording to your php you should have as example this in the html:
<form action="your_php_file.php" method="post">
<p>Your first name: <input type="text" name="FName" /></p>
<p>Your last name: <input type="text" name="LName" /></p>
<p>Your MI: <input type="text" name="MI" /></p>
<p><input type="submit" name="Submit"/></p>
</form>
And the php tags are like <?php
to open, and ?>
to close.
So like:
<?php
if(isset($_POST['Submit'])) {
$FName = $_POST['FName'];
$MI = $_POST['MI'];
$LName = $_POST['LName'];
//....
?>