Find step 4 in getting started on the help center or in the help menu.
Topics is where you have your communication channels in the form of topic boards. Topic boards are controlled by access rights and can be connected to external solutions such as authoring and clash detection tools for a smooth exchange to interest points (clashes, RFI, tasks, clarifications, etc.). These topics can be created and replayed with all necessary object in any other software that supports BCF (BIM Collaboration Format)
Find step 6 in getting started on the help center or in the help menu.