After you've invited participants into the package, you will be able to communicate with them through the Comments Area by clicking on the Comments icon  in any of the requirements.

Once you've clicked on the icon, you will see a messaging box expand below.



You can proceed to click on the Select Person icon , which will provide a drop down list of the participants you can choose to communicate with.



After selecting the participant(s), you can proceed with typing in your comment.  



Once complete, click on Post button and this will leave the comment for the participant(s) when they are viewing the requirement.  In addition, an email notification will be sent to the participant(s) notifying them that a comment was posted to them.



Keep in mind, when the Package Processor(s) needs any corrections or edits to be done to a submitted package, they will use the Comments Area to communicate the correction to you.  You can then follow the instructions here on how to update your package with the newly made corrections or edits.