To add a new one, go to the HTML tab and go to where you want to add the new box.
Always start after the </tr> (after that, make a new line.

Example:

<tr>
<li>Power here</li>
<li>Xats price</li>
<li>Days price</li>
</tr>
<tr>
<li>Power here</li>
<li>Xats price</li>
<li>Days price</lI>
</tr>

etc...