You can either add references in bulk, via databases like Web of Science or PubMed. This is called importing references. The other method is to manually add a reference, for instance if it is a print book, a presentation, or some other document that cannot be found in databases.

Follow these steps to add a reference manually:

• Open Mendeley Desktop.
• Click '+Add new'.
• Select 'Add entry manually'.
• Fill in the form and click 'Add entry'.

You can also add a reference based on the full text PDF:

• Download the PDF(s).
• Open Mendeley Desktop.
• Click '+Add new'.
• Select 'File(s) from computer'.
• Find the PDF(s) in the pop-up window, select them and click 'Open'.

The references will be loaded into your library, incl. the PDF itself. Revise the entry to correct small errors if needed.

You can also edit your references after adding or importing them. You can update them, correct typos, add tags, and so on. Simply look for the reference in your library, select it, and edit the bibliographical information in the sidebar.