Open sqlpara.php and save it as sqlwhere.php. Try it to remind yourself what it does.
On the end of the query (after FROM first but before the semi-colon) add this including the space at the front:
Save and try. The addition to the query tells the server to only return rows from the table where the field firstName contains Fred. You may need to change Fred to one of the names you have in your table if you have been experimenting.
An SQL WHERE statement is how Web sites give a user just the data which applies to them.