1.) Select the entries you wish to export from your EndNote library (you can click one entry, then CTRL click others to select multiple entries at once. Alternatively, you can click one entry and then shift click another to select all entries between those two.)
2.) Click "file" then "export" in the top left of your EndNote application as indicated below.
3.) Name the file "ReadCube Library" and choose to save it as a XML (.xml) file type. Save it somewhere easily accessible.
4.) Drag this file into the import screen using ReadCube Desktop.