There are free and licensed versions of referencing management systems such as EndNote, Mendeley and Zotero. The free versions can be downloaded from their respective websites but they will have limitations to them. Please remember that the free versions may have limited functionalities and you may need to upgrade to a paying version if you need to use the platforms to their full capacity.
Zotero is an easy-to-use tool to help you collect, organize, cite and share your research.