Here are two sample book citations for you to practice manually adding citations to your Mendeley library
Title: The Gamification of Work - Uses of Games in Workplaces
Authors: Emmanuelle Savignac
Year of publication: 2017
Edition: 1st
Publisher: John Wiley & Sons
More information about the book: https://royalroads.on.worldcat.org/oclc/935191857
Title: The leadership challenge : how to make extraordinary things happen in organizations
Authors: J.M. Kouzes & B.Z. Posner
Year of publication: 2017
Edition: 6th
Publisher: John Wiley & Sons
More information about the book: https://royalroads.on.worldcat.org/oclc/982012163
Sometimes you will have to enter your citations manually. In which case: