how to associate category to a sprint or work item

One answer

Category is an attribute of a work item. It is automatically associated to a timeline by its relationship to the project/team area.
If you are not willing to put up with the product documentation, please at least read this: https://jazz.net/wiki/bin/view/Deployment/RTCProcessFundamentals
And tag the future posts with a product name such as rational-team-concert.
Thanks.