Creating a New EndNote Library
In EndNote, select File → New
Select where you want to save the library
Type the name of your new library
Click the "Save" button
This tutorial from the EndNote Training YouTube channel demonstrates the steps for creating a new EndNote library and for backing up an EndNote library.
More Details About Libraries
Libraries have two parts: a file with the extension .enl and a folder with extension .data.
The .data folder will contain file attachments, term lists, and citations.
The number of references you can have in a library is unlimited - but it is best to keep it under 100,000.
You can create any number of libraries, but you can only sync or share one of them using EndNote Basic
Libraries created on a PC can be used on a Mac, and vice versa.
It is very important to periodically back up your EndNote libraries. To do this in EndNote, select File → Compressed Library (.enlx) and follow the prompts.
Storing EndNote libraries in cloud-syncing folders or keeping read-write EndNote libraries on network drives or flash drives, can corrupt the data.