There are 2 ways of selecting the font for your website:

1. The easy way: Using the preset fonts selections that we provide.

We provide font selections that go well with our themes. When customizing a theme, you can select the fonts that you want to use, and you can also select the font size, weight and letter spacing.

From the Menu on the Theme Customizer, simply click Design > Fonts.

2. The other way: Use whatever web font you want.

ArtStation Premium accounts offer CSS overrides. This enables you to use the @import statement to import any web font that is available online via services such as Google Fonts and Typekit.

More details on this here: Custom CSS Overrides.