Communicating with other project stakeholders is an important part of the design process. In the platform, there are 2 types of communication available within the schedule:
Comments - General communication can be placed under comments, which can be accessed both from the summary tab of the project, as well as any view of the schedule.
RFIs - Specific Requests for Information should be placed under the RFIs section of comments, which can also be accessed both from the summary tab of the project, as well as any view of the schedule.
For more on working with comments and RFIs within a project, take a look at the video below: