Rachel here from the Shopify Guru Team!
If you want to change your store name at the top left of your store, you can head to Settings > General and change your store name. From the theme section, you can click on the Header section in your Customize Theme Editor and replace that with a logo. Here's a tutorial for editing your header for Debut. If you want to change your store name in the meta description of the store, you can head to Online Store > Preferences.
I hope this helps, but if you have any further questions - be sure to reach out to Shopify Support!