Increase font in header

Hi all! My website is http://www.tranquilidad365.com.do. I would like to increase a bit the font of the description: “Seguro contra enfermedades catastróficas en República Dominicana – Cobertura de RD$1,500,000 en efectivo – Un producto exclusivo de Mapfre BHD y Marisol Lama & Asociados”.

How can we do it?

Thanks!!

[Moderator Note: No bumping. If it’s that urgent, consider hiring someone.]