Dallas here from the Social Care Team here at Shopify.
I, unfortunately, am not able to give direct assistance with this customization since it is a third party theme as you say. However, I wanted to point you in the best direction.
Have you reached out to the theme developer yet? They might just be able to do this customization for you and to be honest it might be the simplest option since they'll know the back end of their theme the best.
However, if they don't then you can also reach out to the Shopify Experts who should certainly be able to go in and look into making your desired adjustments.
Those will be the steps that you want to look into.
If you have any more questions or need more assistance please let me know.
We love to help you.
Please contact us at: https://www.mswebdesigner.com/pages/contact-us
Thanks & Regards
MS Web Designer