It is hard to know where to start since you provided quite little context ??

I assume that you are developing a custom theme or child theme. Is that correct?
If that is the case, in the template that you want the tagline to show on you can use the following code to print the tagline

<?php echo get_bloginfo( 'description' ); ?>

Is that what you were asking for?
Let me know if you need further help ??
Cheers

Here’s some more context (sorry about that!)…

I’m building the site using Genesis + the Infinity Pro child theme. Right now I’ve got my clients site name dialed in but we’d like to be able to include his site tagline below that in the header.

Would the code you provided make this happen? If so, would I simply add it to the end of the functions.php file?

I understand that Infinity Pro is a paid theme, and as such it is not supported in this forum.
You should reach they support since you are paying for it.

Nevertheless, I’ll give you a clue for free ??
Try adding this custom CSS:

.site-header .site-description {
    text-indent: 0px;
}

You will need to figure out the rest of the styling with Infinity Pro support.

Take care!

I find it hard to believe a paid themes that didn’t come with a site tag line.