From within the EndNote library click on the icon in the menu to access the help manual.
The Little EndNote How-to Book is an e-book of instructions on how to accomplish specific tasks in EndNote, such as importing references from a specific database or converting references from another program to references in an EndNote library.
Look under Training for live training sessions, online tutorials, and the full online manual which you can download.
EndNote has a training channel on YouTube - www.youtube.com/endnotetraining
This site has lots of video tutorials on how to do most functions in EN. Some are short tutorials on how to do a specific task e.g. exporting from PubMed, others are longer class recordings of their webinar class sessions.