The module makes full use of Drupal's API and hooks and works nicely when multiple widget instances are used.
Unpack in your modules folder (usually '/sites/all/modules/')
Enable under Administer > Site Building > Modules
Here are some key features of "YUI Form elements":
- AHAH integration with calendar widget (on 'change' event only)
- Easy to use. Some samples are provided in Drupal's modules administration pages.