Services like Dropbox let you create a download URL for any files you have.
You can use those links to upload files from DropBox directly to TalentLMS.
The only thing you need to do is go to DropBox, select the file you need, and click share.
Then click the “Create link” option (or skip this if you have already done it before), and afterwards select “Copy link”.
After copying the URL you can upload your dropbox file to your TalentLMS course in two steps:
Go back to your course's content and add a Presentation/Document Unit (3) and then select to "use a document from your files" (4) and select the dropbox file.