Check in with students that are not participating.   Find out if it's technical difficulties, not knowing the guidelines, etc.  Monitor discussions and make sure they are appropriate.

If you hold synchronous sessions, provide students information prior to the chat session to better prepare them.  To promote confidence and participation, provide feedback.  

Communication and regular discussions will make your students feel supported.  Posting a biography about you and having your students post a short biography about them will help build trust and relationships.  If you don't know the answer to something, it's okay to share that, but always say you will find out and follow up with that promise.

Being there to support your students through this process is very important.  They can get frustrated so be available to assist.  Also, before assigning online lessons, provide an orientation to explain how the process will work. :)