Try a better alternative which also bulk downloads papers and pulls in the bibliographic details from the Web. and then autotags papers, and finds themes automatically. It is Qiqqa.
Having explored YouTube videos, I finally took a short course in Udemy. It is called " Complete Mendeley Course for Researchers & Students". The faculty is Dr. Christa van Staden. I found it very useful and am happily using Mendeley.
As well as, Udemy course entitled (Reference management tools using Mendeley) is very interesting to let you know and efficiently use Mendeley and its functions.
Hala Adnan Hashim, you can learn about Mendeley and other software management programs here: https://www.aclang.com/blog/management-software-for-academic-scholars/