Thank you for your interest in UI for NativeScrtipt
If I understand you correctly, you would like to populate the RadCalendar component with data and to change the selection mode of the component.
Regarding the first question, you could review this article
, where it is described, how to define a list of events. For further info, you could also review the sample here
The calendar component supports several selection mode options: Single, Multiple, Rane, which are described here
and their usage is demonstrated in this sample app
However, if the case is different, please provide some more detailed info about your scenario.