To upload documents to the personal files from the cloud memory, first click on the personal files and open the "Documents" column. There you will find a "+" button to the right of "Actions".
Clicking the "+" button opens a window where you can choose whether to upload a document from the local files or from the cloud storage. Click on "Cloud Storage".
This opens another window where you can select the various cloud storage services and redirect them to the page.
After selecting the document, you can upload the document using "Save".