Create a new PHP page from your template. Save it as sqlinsertwithcode.php. In the middle chunk of PHP (currently empty) put this line:
mysqli_query($dbconnection, "INSERT INTO first (personalName, familyName) VALUES ('Fred', 'Bloggs');") or die("Error inserting: ".mysqli_error($dbconnection));
As before this is the PHP function which sends queries to the SQL server. The query is in the quotes. The table name is first. Note that the first set of brackets is the field names you just created and so have no single quotes around them. In the second set of brackets are the values to go into those fields. These are text and so need to be inside single quotes. SQL uses single quotes.
Save and try the page. It should be blank (the or die bit will tell you if anything goes wrong). Refresh it. The code has just inserted another record into the table and each time you refresh you will get another identical record (row) in the table. Change the code to insert a different pair of names to make three in total (the first two being the same).
You will display those records soon.