[Theme: Mantra] How do I center the title of a particular page?

For the life of me I can’t figure this out, the theme has a custom CSS field, I’m hoping I can use that instead of jumping around guessing at what file I need to edit. I thought it may be the Content-Gallery.php since the page is supposed to be a gallery. No luck no matter what I do, it’s a simple thing but this theme is different somehow.

Biggest thing is that I need to know how to target one page, all the forums I’m running across are about the title in the header, or the presentation page. I’d need to know exactly what line to use if anyone knows, I’m still learning.

Thanks in advance