Please, advise how to change the font size of the site title and tagline.

I have gone into Appearance-> Customize -> Additional CSS. I just don’t know the code to use.

I have tried a few different codings (see below) but they have not worked. My theme is Agency Starter not sure if that makes a different.

—————————————-
p.site-description {
font-size: 20px;
}

————————————————————————————————————————
.frontpage-banner.image-banner .block-title {
font-size: 45px;
}
.frontpage-banner.image-banner .description {
font-size: 30px;
}

————————————————————————————————————————

.site-description {
font-size: 14px;
}
————————————————————————————————————————

h1.site-title {
font-size: 35px;
font-style: italic;
color: #000;
text-shadow: 0 0 4px #FFF;
}

.site-description{
font-size: 15px;
font-style: italic;
color: #000;
text-shadow: 0 0 4px #FFF;
}

The page I need help with: [log in to see the link]