Installing individual Styles or Style Packs is simple.
After purchasing and downloading Styles from the Capture One store, go to Adjustments -> Styles -> Import Styles and select Styles or a Style Pack from your downloads folder or another destination.
The steps are the same on Windows.
NOTE: Capture One Styles are only supported with Capture One 10.1.2 and newer versions of the software. Nordic & Beyond Styles can be used only in Capture One 20 and later versions.