The most basic way to enter a reference is by typing it in. Click References-->New Reference.
Here are some tips to keep in mind when manually entering a reference:
You can import PDFs into your EndNote library. Not only that, but EndNote can create a reference using the PDF's Digital Object Identifier (DOI). If the DOI is not present the PDF will be imported, but you will need to do manually enter the reference information into EndNote.
Most of the Georgia State University Library's databases, including GIL-Find, the catalog, support the direct export function. This is the easiest and most efficient way of adding references to your EndNote library. Every database works a little differently, but most databases can export to EndNote with these general steps: