EndNote automatically saves, or prompts to save, references every time you add or edit one in your library, but to make a copy of your EndNote library it is recommended to create a compressed library. EndNote libraries can be big and are composed of multiple files. Compressing the library creates a smaller, single file that can be more easily stored, moved, or emailed.
To create a compressed copy of an EndNote library go to File > Compressed Library (.enlx)...
Select the appropriate options and click Next, select where to save the compressed library and then Save.
It is recommended to have a single EndNote library to store all your references, and only one library can be synched with the online version of EndNote. However, you can create multiple EndNote libraries if needed.
To create a new EndNote library go to File > New and then name the library.
References collected and created in EndNote as well as associated files are referred to as libraries. When EndNote is launched for the 1st time you will be prompted to create a default library.