Use your client area to get the URL for your rutorrent server, along with username and password
Use Digest Auth instead of basic auth while setting up your server.
In the "FTP/VPN Details" tab, click on the "Direct HTTP Access" button to get the base URL for HTTP Downloads.
Please note again to use Digest Auth and not basic auth while setting up HTTP downloads.
You can find the hostname, username and port listed in the admin area. You will have to connect via filezilla or an SFTP client to get the folder for the downloads:
Here, you can see it is
/downloads/manual, but it might vary according to seedbox.