If you need the ability to upload files from your Synology, there is a simple ftp client built in to DSM 5.0 and higher.
You can find it in the “File Station” application under “Tools” > “Remote Connection”
From there, select “Connection Setup” and select the desired option (ftp in my case).
Enter the info corresponding to the ftp account created for you at the remote ftp server
The ftp location will be added to the file navigation section under “FTP” and will become a valid “Copy to/Move to” option in the right click menu for files displayed in File Station.