SYM-events should be placed in the MATH departments event-folder with the tag "SYM" added. Please remember to include the tag "SYM" as the event will otherwise not appear in the SYM calendar.
To add or edit an event you need to log into the CMS. See MATHnet Calendar page for username and password to the calendar - or use your own, if you already have access to the CMS.
Log in to the CMS and Add an event.
See the Manual to MATH Calendar (pdf).