Your site title and tagline let your visitors know what kind of content and service to expect from you.
For guidelines on how to choose these, refer to this article.
To change your title and tag line go to DASHBOARD > APPEARANCE > CUSTOMIZE > SITE IDENTITY
Next you’ll see this section.
Click on the arrow icon then type your business name and tag line in their respective areas and save. Please note that these will only show up if you do not set up a logo.
If you upload a site icon, it will be used as a browser icon for your site. It should be exactly 512 x 512 pixels.