Store Logo

You can adjust the size of logo to fit with your site

In the Admin panel -> go to Storefront -> Logo

Also, here is an article of BigCommerce for your reference: https://support.bigcommerce.com/articles/Public/Uploading-a-Custom-Logo/

If you want to use text to make your logo:

In the Admin panel -> go to Storefront -> Logo

If you want to use logo title here, please do not enter text logo title in Editor.