The config.yml file in the Freshman21 theme includes five parts.

First part is the site info. 

title: Freshman21 # blog title
tagline: Another Jekyll theme, Freshman twenty-first # blog sub-titile
author: Lijia YU # author name
email: yu@lijiayu.net # author email
description: "Freshman21 is a Jekyll blog theme." # You can edit this line in _config.yml. It will appear in your document head meta and in 
your feed.xml site description
keywords: "Jekyll, theme, Freshman21" # html meta keywords
baseurl: "/freshman21" # the subpath of your site, e.g. /blog
url: "http://yulijia.net/freshman21" # the base hostname & protocol for your site

Part 2, Personal info and site tools info, twitter, github, aboutme and aboutme_photo only appears on the sidebar aboutme-box, you can Hide in two ways [1]:

twitter_username: #your twitter handle  
github_username:  #your github account
disqus_shortname: #disqus shortname
favicon:     "images/favicon.ico"
aboutme: Hi, this is Lijia Yu. I made the Freshman21 theme. Please enjoy it. # these are shown on aboutme-box(sidebar).
aboutme_photo: https://i.imgur.com/15BT1.jpg # your personal photo.

Part3, Site setting:

ShowContactInfo: "True" # Personal Info (twitter,github,email) can be seen on aboutme-sidebar, those info only shown where ShowContactInfo == True
default_column: "two" # blog style: two columns, if default_column != "two", you will see a one column blog.
default_locale: "en" # blog sidebar language set, only include: English(en) and Chinese (cn)

Part4, Blogroll info, only name tags can shown on the page.

Blogroll:
      - name: Freshman
        href: http://yulijia.net/freshman
        title: Another Jekyll blog theme
      - name: author's website
        href: http://yulijia.net/
        title: Lijia Yu's website

Part5, Build settings

markdown: kramdown
highlighter: pygments # highlight
paginate: 5  # how many post can seen in the main page

=====

  • [1], you can set those info at Part3 or just delete the aboutme.html at sidebar.html in _include folder. 
<div class="col-sm-2">
  <!--{ % include Aboutme.html % }-->
   { % include Copyright_Notice.html % }
   { % include Recent_Posts.html % }
   { % include Categories.html % }
   { % include Tags.html % }
   { % include Blogroll.html % }
   { % include Archives.html % }
</div>