This are the minimum settings you need in _config.yaml:

#
# Site basics
#

#
# NB. ALWAYS add a forward slash to the beginning of root-relative directories - that's how it knows you're referring to a file or URL.
#

title: Your Site Title
description: A description of your site.
defaultAuthor: Your Name
prodUrl: https://yoursite.com
copyrightStart: 2018            # First year of copyright.
headerLogo: /assets/images/your-header-logo.png
postsPerHomePage: 30

#
# Site Publisher
#
publisher:
    name: Your Organisation Name (or site name)
    logo: /assets/images/your-organisation-or-site-logo.png
    url: https://yourorgsite.com
    description: A description of your publishing organisation.

#
# Site Authors
#
authors:
    Your Name:
        name: Your Name

#
# Words per minute read time.
#
wpm: 250

A better, more complete version would look like this:

#
# Site basics
#

#
# NB. ALWAYS add a forward slash to the beginning of root-relative directories - that's how it knows you're referring to a file or URL.
#

title: Your Site Title
description: A description of your site.
defaultAuthor: Your Name
prodUrl: https://yoursite.com
copyrightStart: 2018            # First year of copyright.
headerLogo: /assets/images/your-header-logo.png
postsPerHomePage: 30

# Other images that represent your site.
image: [/assets/images/img1.png, /assets/images/img2.png]

# A default image for articles that don't have any images.
defaultArticleImage: /assets/images/default.png


#
# Site Publisher
#
publisher:
    name: Your Organisation Name (or site name)
    logo: /assets/images/your-organisation-or-site-logo.png
    url: https://yourorgsite.com
    description: A description of your publishing organisation.

# Another image for your publisher in addition to the logo.
    image: /assets/images/gordys-discourse.png

# Some of your links online.
    sameAs: [ https://www.facebook.com/yourid, https://twitter.com/yourid ]

# Social media IDs.
    facebook: yourid
    twitter: yourid

#
# Site Authors
#
authors:
    Your Name:
        name: Your Name

# An image for you, the author.     
        image: /assets/images/hat-ga-768x768.png

# Some of your links online.
        sameAs: [ https://www.facebook.com/yourid, https://twitter.com/yourid ]

#
# Words per minute read time.
#
wpm: 250

Configs Index