Creating a season is a pre-requisite to create products.
If you wish to keep key items from the existing season
If not, you can just click on NEW to create a new empty season. The season has start and end date. The sales can start prior to the season start, but you will not be able to create a product that has a date before the beginning of the season. The season dates particularly matter if you sell memberships or passes that are valid every day the season in which it is sold.