To customize theme typography navigate to Appearance > Customize > Typography to start customizing the theme Typography.
Here you can control Typography options such as Font Family, Font Weight, Font Size, Line Height, Font Color.

- Headings & Body
Customize H1-H6 headings and body typography in this section. - Menu
Customize theme Main Navigation typography in this section. - Breadcrumbs
Customize theme breadcrumbs title typography in this section. - Button
Customize theme buttons typography in this section.