Where are the earlier episodes of my podcasts?

I just downloaded version 12.4.3.1 of iTunes on my HP 2000 laptop. I've got a problem with the podcasts view. Suddenly, I can only see the last edition of my podcasts, and when I click on the icon that represents a particular podcast, the last episode automatically plays. Do I have to go to iTunes Store to download earlier podcasts? And if I do that, where do I find them in iTunes?

Kelly