Create a completely empty page called formandprocess.php.  Put this into it:

<?php
    error_reporting(E_ALL);
    ini_set("display_errors", TRUE);
	
    if (!$_POST) {
		 
        echo "not submitted";
	
    } else {
	
        echo "was submitted";
	
    }
?>

Try it and the results should not surprise you.  The if statement can be read as "if the $_POST superglobal does not exist".  It is "does not" because of the exclamation mark as explained previously. 

How to get the HTML page and form

You will soon need to put the form in to replace the first echo line but first an explanation of how you will do it (and another way).  There are two main ways to do it:

The second choice is far simpler (look for the original if/else and spot the HTML inside that):

<?php
    error_reporting(E_ALL);
    ini_set("display_errors", TRUE);
    
    if (!$_POST) {
        ?>
    <!DOCTYPE html>
    <html>
        <head>
        <meta charset="UTF-8">
        <title></title>
                  
        </head>    
        <body>
        <h1>A form</h1>
        <form method="post" action="https://www.yourwebskills.com/files/examples/process.php">
            <label for="text1">Your user name: </label>
                <input type="text" id="text1" name="text1">
            <label for="text2">Your password: </label>
                <input type="password" id="text2" name="text2">
            <input type="submit">
        </form>
        </body>
    </html>
    <?php
    
    } else {
    
    echo "was submitted";
    
    }
?>

The other method is more powerful because it allows you to use variables within the form.  At the moment that may not matter but it will later.  The problem is that you need to escape all of the quotes:

<?php
    error_reporting(E_ALL);
    ini_set("display_errors", TRUE);
    
    if (!$_POST) {
     
    echo "<!DOCTYPE html>
    <html>
        <head>
        <meta charset=\"UTF-8\">
        <title></title>
                  
        </head>    
        <body>
        <h1>A form</h1>
        <form method=\"post\" action=\"https://www.yourwebskills.com/files/examples/process.php\">
            <label for=\"text1\">Your user name: </label>
                <input type=\"text\" id=\"text1\" name=\"text1\">
            <label for=\"text2\">Your password: </label>
                <input type=\"password\" id=\"text2\" name=\"text2\">
            <input type=\"submit\">
        </form>
        </body>
    </html>";
    
    } else {
    
    echo "was submitted";
    
    }
?>

​You could also echo each line separately if you wanted to.  How you do it will be your choice.  Here I will turn PHP on and off as needed to make the examples shorter!