If you have questions about using mojoPortal, you can post them here.
You may want to first review our site administration documentation to see if your question is answered there.
Is there a way I can find how many, if any, users are active on the site at any time? I need to close the site occasionally and would like to know whether that would inconvenience any user that is logged in at that point.
If you are tracking the site with google analytics, then you can login to google analytics and view the real time reports to know how much activity is currently going on.