You'll find this field in the 'My Packages' tab when you hit 'Create Package' or 'Edit Package'.
When your client logs in, the content you add here will show on the first page of the Client Dashboard - so this is a great opportunity to make a good first impression.
You can add images, text, even a short video if you really want to and create a whole 'Welcome Page' with this area.
Or you can keep it short and sweet and just give a basic introduction to your package and a reminder of what your clients can expect to achieve by working through your content.
Here's an example of what you might like to create.
Tip: If your client has purchased more than one package from you, they will see all of their packages from you listed on their client dashboard and will need to select which one they want to work on today. It helps therefore, if you create a consistent 'look and feel' to all your Package Descriptions.