To change the WordPress site title and tagline, navigate to SETTINGS then to GENERAL.
This is the General Settings screen.
To change Site Title, type on the field provided.
To change Tagline, type on the field provided.
You can also change other details on this page like the Admin Email Address, Membership Type, Time Zone, Date Format, Time Format and Week Starting Day.
After the entries or changes, be sure to click on SAVE CHANGES.
WordPress will give notification that the settings are saved.