First, if necessary, create a new feed (from the Browse Content menu) to hold the content, and add it to the required display(s). Then create the content using the normal Add Content page. Using the ticker tab:-
- Insert some placeholder text. Anything will do, it is easier to insert the correct text later
- give it a sensible name
- set the start and end times, typically ending far in the future
- set the duration, typically 3600 seconds (1 hour) for a calendar. Note you CAN'T change this later, so make sure it is correct
- add it to the required HTML/TEXT feed that you possible created earlier.
- change the type_if field from 2 to 1
- then insert the html you required, typically and iFrame, into the content field and press go.