See D2L help pages from National Louis University. In particular, the sections titled Set up integration with a tool provider and Set up a link to a tool provider are relevant.
Kutztown University has also put together a series of videos for Curriculum Builder in D2L, including how to use it and set up of the tool. Please note that these videos show the first version of Curriculum Builder, and that Custom Parameters are no longer required during set up, and many new features have been added to the tool.
Document Download: D2L Instructions
A special thanks to Julie Wolfe and Chaya Merrell at Bloomsburg University of Pennsylvania for documenting how to install Curriculum Builder in Desire2Learn!