Firstly, you can download package here.
sudo dpkg -i <path-to-downloaded-package> sudo apt-get update sudo apt-get install mendeleydesktop
Now you have Mendeley on your computer.
Let's add the Microsoft office (or Libre office) citation plug in.
1. Drag and drop paper's pdf file, which you want to cite to your thesis, to Mendeley
2. In your office writer, "Insert citation" for citing in text body.
3. In your office writer, "Insert bibliography" for citing in reference.
4. You can select the citation style through office writer.