1. From Customize section, go to Site Identity.
2. From Site Identity, you will be able to add various options related to site identity like:

• Logo: It changes the main logo of the site.
• Site Title : It changes the main site title of the site.
• Tagline : It changes the tagline (i.e:Description) of the site.Just below site title.
• Display Site Title and Tagline: This enables/disables the site title and tagline from the site
• Site Icon : The Site Icon is used as a browser and app icon for your site.Icon must be square and at least 512px wide and tall.