Struggling to invite others to a meeting I didn't organize

Hi.  Another manager at my company scheduled a webinar, then she left the company.   I now have our license.  I am trying to invite others to the meeting she set up.  I was invited to that meeting and responded, but I cannot invite others to it.  it is not showing up on my calendar under UPCOMING MEETINGS.  Further, my homepage says CONNECT YOUR CALENDAR OR SCHEDULE A MEETING.  I am unsure how to connect my calendar.  i cannot change dats as it is "greyed out."