Slider Text Not Responsive

Hello. I’m working on https://primarychoicehomes.com/.

I wasn’t sure what to put in the home page slider description field. I copied this code from the theme’s website here

So here’s what I have:

<h1>Tired of making your landlord rich? <h1>
<p>Become a homeowner!</p>
<p><a href="#" class="btn-slider"></a></p>

But the text is not responsive, ie – it looks too small on my computer screen and too large on my phone.

Can you point me in the direction of some simple code to make these headlines responsive to screen size?

Thank you. Rachel.