When you are in a session or meeting – whether it's a breakout or broadcast – you will be able to add session segments.
First, scroll down the Session details page until you see "+ segments".
Then, click on Segments and follow the prompts on the segment module. You will be able to add a title for the segment, the duration of the segment, and the speakers for each segment (you will only be able to add a speaker to a segment if the session you created has speakers added to it.)
For each segment, you'll have the ability to reorder the segments and save those changes.