In order to manage Blog Popular Posts in Magento 2 Blog, please go to the Admin Panel > Stores > Configuration > Magefan Extensions > Blog > Sidebar and find Popular Posts Widget section.
Popular Posts Widget
1. Enable or Disable the widget
2. Specify the Number of Posts you want to be displayed in the Popular Posts.
3. Set the Sort Order to manage the position of the widget on the Storefront. The higher the number of the position, the lower it will be displayed on the Sidebar.
Once you've finished don't forget to Save Config and Flush Magento Cache.
4. Check the blog Popular Posts out on the storefront.