How to add multiple divs on top of already existing div class? [closed]

I want to add the following 2 divs on top of already exisitng div using javascript.
How can I do it? I am sure its something basic but I cannot seem to figure it out.

This is how it looks:

<div class="agenda">
<h2>Test Data</h2>
<p>This is my text<.p>
</div>

This is how I want:

<div class="grid-container">
<div class="grid-row grid-gap">
<div class="agenda">
<h2>Test Data</h2>
<p>This is my text<.p>
</div>
</div>
</div>