Retrieve data from database to textbox wordpress - php

Question

I need to fetch data from PHP MyAdmin database to WordPress website page. Since I am new to WordPress I am not too sure which method I have to follow. I tried to edit the source code of the page by adding the new PHP code inside PHP tags. But it did not work. And I found a file named 'functions.php' in the local directory where my project located. Is that the file I need to use this code? I've already written the code and I just need to know where to use it.
<?php
$results = $wpdb->get_results( "SELECT * FROM $table_name"); // Query to fetch data from database table and storing in $results
if(!empty($results)) // Checking if $results have some values or not
{
echo "<table width='100%' border='0'>"; // Adding <table> and <tbody> tag outside foreach loop so that it wont create again and again
echo "<tbody>";
foreach($results as $row){
$userip = $row->user_ip; //putting the user_ip field value in variable to use it later in update query
echo "<tr>"; // Adding rows of table inside foreach loop
echo "<th>ID</th>" . "<td>" . $row->id . "</td>";
echo "</tr>";
echo "<td colspan='2'><hr size='1'></td>";
echo "<tr>";
echo "<th>User IP</th>" . "<td>" . $row->user_ip . "</td>"; //fetching data from user_ip field
echo "</tr>";
echo "<td colspan='2'><hr size='1'></td>";
echo "<tr>";
echo "<th>Post ID</th>" . "<td>" . $row->post_id . "</td>";
echo "</tr>";
echo "<td colspan='2'><hr size='1'></td>";
echo "<tr>";
echo "<th>Time</th>" . "<td>" . $row->time . "</td>";
echo "</tr>";
echo "<td colspan='2'><hr size='1'></td>";
}
echo "</tbody>";
echo "</table>";
}
?>