Support for seasons was introduced by Apple as a convenient way to organize episodes within a series. If you choose to use seasons, the Apple Podcast App will organize your episodes by season:
If you haven't set up seasons and would like to, you’ll first need to turn seasons on in the Episode Organization card on the Series Detail page. This will create a new Seasons card on your series dashboard, from which you can create new seasons. Finally, using the ART19 Episode Organization Tool, you can add existing episodes to newly created seasons in bulk. This process is explained later in this article.
Creating a Season
Step 1: Enable Seasons
On the left side menu bar, navigate to Seasons and then click "Enable Seasons."
Step 2: Create new season
Click on the plus sign 
located in the top right corner. Select a season number and a title. Just to note, season titles will only be seen in ART19 and will not be viewable on listening platforms.
Adding Season Numbers to Existing Episodes
Once you've turned on Seasons, you can add existing episodes to seasons by using the ART19 Episode Organization Tool. Follow the steps below:
Step 2: Navigate to the Episode Organization tool
Select Episodes on the left side menu bar, and then click on the number sign
to navigate to the Episode Organization page.
Step 3: Renumber Episodes
Renumber your episodes either by manually going through and selecting season and/or episode numbers accordingly, or use the dropdown box on the top left to select more than one episode and apply your season change to all of the selected episodes.