Save the generated file in the same folder as your LaTeX document.
If you are using Overleaf, go to your project and click on the Upload button, then select the .bib file to add. You can rename it at any point, but ensure that the file is saved with extension .bib.
You can add references from your existing BibTeX file into your Mendeley account.
Review the newly imported collection to ensure all references have been added correctly.