The current version of Things for iPhone does not yet support repeating tasks. But we are working hard on adding the missing features. Things for Mac already has a very nice and powerful implementation of repeating tasks. And Things for iPhone will of course get this feature too.
In the Mac version, repeating tasks are "templates" that remain in your Scheduled list. These templates regularly create new copies and add them to the Today list. The templates themselves are not synced to the iPhone, but the copies in your Today list are synced.