When you begin to add any kind of breakout session to your event, you will want to navigate to Sessions, which is located under Activity Management. You will want to be sure that prior to adding any sessions, you have already loaded your Schedule and your speakers so that the Session information will be complete.
Loading Sessions are pretty simple - just click on the green Add Session button and then fill out the required information. This includes the title of the session, location and time slot, and the speaker. You can fill out the session description and tags (which will show up on your event page) or you can allow your speaker to fill out those further details.
Once you get your sessions loaded, you can then manage the sessions from the main Sessions page. The drop down list gives you the option to View the Session Page (which shows you what it looks like on the Event page), Upload Session Content (this allows you to load session data to the Content section of your website), or Delete (which allows you to delete the session if it is no longer needed).
You will also notice that your session is either Published or Draft mode. This feature allows you to get your sessions in place, but wait to publish them to your event page. You can simply Save them as a draft.
Once you have completed your Session additions, be sure to go back to the Speakers tab and Invite Speakers now that you have their sessions in order. See the Speakers article for more detail.