"Stellar Church WordPress Theme"
— ChurchMag What They Say

Can I change the homepage intro font size?

The intro on the Homepage is intended for a prominent one or two line introduction as shown on the demo. We recommend something brief to introduce your church while having a separate page for full information. Keep in mind that readers are not likely to read much text on the homepage of a website. The homepage is a gateway to pages with content.

If you still do want to change the font size, you will need to use custom CSS code.