Click on the Managed Vessels option in the My Account section. A list of your managed vessels will be displayed under the Managed Vessels tab. Click on the Manage Documents button which is located at the right end of each vessel's row. Each vessel has her respective button.
Depending on the vessel of your choice, the already uploaded documents will be displayed. Click on the Add Document button to upload a new Document regarding the subject vessel.
A form will pop-up that will enable you to upload a new Document and define its properties. 
Thus, you are able to provide the following information regarding the document you wish to upload:
- Document Type (e.g. Certificate of Registry, Document of Compliance)
- Document Title (auto-completed upon selection of the Document Type - editable field)
- Issuer Name
- Security Level
- Date Issued
- Expiry Date (Document's "Valid Through" date)
- Expiry Reminder Threshold (depending on your selection, you will get notified prior to the Document's Expiry Date)
- Comments
Click on the Browse button and locate the Document you wish to upload.
Finally, when you are ready, click on the Submit button. Your Document will be uploaded and displayed along with any other uploaded documents referring to the subject vessel.