You can select the tr:first element and than .after() to add your new element:
$('table tr:first').after('<tr><td>00001</td><td>John</td></tr>');
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
<tr>
<td>00002</td>
<td>David</td>
</tr>
<!-- Here is where I want it to be insterted -->
<tr>
<td>00004</td>
<td>Frank</td>
</tr>
<tr>
<td>00005</td>
<td>Jane</td>
</tr>
</table>