How do I periodically import from a source? In the basic settings of a feeds importer there is a select list:

Periodic import
Every 30 min
Choose how often a source should be imported periodically. Requires cron to be configured.

Merely selecting an option doesn't appear to import from my source every 30 minutes. It appears that I have to configure cron too. I've found a lot to read about this, but nothing that describes the basics.
What do I need to do to ensure my source is imported periodically? I can do a manual import without problem.
For periodic import of feed, you have to configure cron.

Let say you want to import feed in every 1 hour then configure cron to run after every 1 hour too.

In Drupal 7 you can enable cron via the Administration > Configuration > System > Cron (admin/config/system/cron).

For more information cron setup visit here