In the basic settings of a feeds importer there is a select list:
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.