From the Speaker portal, click on My Sessions:
From there, click on the name of the session you wish to view:
The next page gives you a view of your session. From here, you can make edits to the session as needed. Remember to click the Save button at the top of the screen when you're finished:
Please note that sessions can be locked by event Admins (notice the lock icon above), which will prevent non-Admin users from editing the session. If you are a Speaker, and you see the locked symbol, you will not be able to edit the session.