This feature requires third-party advertisers option to be enabled in settings page and WooCommerce to be installed.
In order to create a package navigate to Products → Add New
Select AdCenter Package and in general options you will get following fields-
Regular Price and Sale Price
Package Type - Cost Per Days (CPD), Cost Per Clicks(CPC), Cost Per Impressions(CPM)
Duration/Clicks/Impressions - Depending upon package type
All the packages created will be shown in WPAdCenter → Packages as such