Use Cookie Editor in Firefox to copy the PHP Session ID of your Wupload account. Then you could add this cookie to Cookie Manager of MU.
Remember that the cookie is not permanent, it will expire after a few days or weeks. You must update when it generate the new cookie
Here is an example
Domain name: .wupload.com
Cookie name: PHPSESSID
Cookie Value: 1820geva74o9123iosifeaiu10ret51
Remember to add the description is the filename when fetch links to MU because the MU cannot catch the correct filename for Wupload.
The same rule apply for Filesonic and other host that base on Cookie.
Hope this help!