First go to the Organization level Send Emails page from the navigation menu in the upper left:

Next, select "I want to include reports", choose which assessment data you'd like included, and then select the players you want to send reports to, just as you would at the assessment level.
Click "Create Message" at the bottom of the page.

Then, on the create message page select "Include Player Development Reports" in the Report Configuration section.

Then feel free to compose the message just as you would from an assessment.