It looks like you are using a checkout of the
master branch, because the code you posted is not yet available in any of the releases. It will go out with v3.2 early in the new year.
That code supports one of the theme options for the default theme. If you are using the default theme, you can go to Settings > Website > Appearance > Theme and you should find a theme option checkbox for Journal Description that says:
[ ] Show the journal description on the homepage.
Check that box and save the settings. You should then see the Journal Summary appear on the homepage. If it doesn’t, you may need to fill it out by going to Settings > Journal.
(Note that this is the short Journal Summary, not the full About the Journal section. I’ve seen the discrepancy in language here and we’ll update the theme option to use the phrase “journal summary”.)