The usual way to move a file from your computer to Voyager is by using a program designed for the purpose. You need to be able log into your Voyager account and transfer the file by placing a copy of the file in your directory on the Voyager server.
There are some suggestions for free Mac applications here
Fetch is an old friend. I have used it forever.
Technically, an FTP application is pretty simple – log in, display directory contents, move files from here to there,… Any of the ones that are free and appear in multiple “best” lists will do the job.
Do you have a favorite ftp application or service? Is it for Windows or Mac or cross-platform? Best features?