I have Use Cases saved in DNG and I'd like to Bulk load them as User Stories in RTC, while creating links between the two.  I see how to do this one at a time but can it be done in bulk?

in DNG you need to store the requirement artifacts (use cases) in a collection or a module.

in RTC you need to create a plan.

in the plan you open the links tab
from add link choose the relation implement requirement collection
select the collection or module from DNG

now you can in the plan on the link tab open the collection or module and create one RTC story for each use case

take care to press the save button on the RTC side.

in addition to the steps Robert outlined, you may need to have RTC configured to create stories from the collection (or module).  I think it may be the default setting but I remember we had to switch ours from "Epic" to "Story", but we are still on 5.0.2 (upgrade planning in process).

the default setting within the IBM build in process template is a mapping to a story, even in the older versions.

Nevertheless it is a good point to check this settings:

administration, manage this project area, work items, change management type binding, implementation request to: story.