I’m sure we can help you here. Please first specify whether you’re asking what happens in RW (which version are you using?) when you publish and/or how to upload a locally-published site via a third party client such as Transmit; it’s common practice for RW users to resort to independent upload like this when publishing fails.
One initial bit of clarification: during the early days of the internet (say, 1970’s and 1980’s) its pioneers based a lot of the architecture on what was (and really, what remains) the most reliable network protocols (the ‘rules’ for connection, transfer, delivery etc) on Unix.
On Unix machines files were moved from one machine to another using ‘File Transfer Protocol’. Because intended for moving files between local machines, and before scammers, spammers and generally ill-intentioned people, FTP became inappropriate (because it is not secure) for the kind of file transfer needed on a Wide Area Network like the internet, which you use to get your website’s files from your Mac to your host. So SFTP (SSH File Transfer Protocol, where ‘SSH’ is the currently most used and most secure way to connect machines because data passed between them is encrypted) was developed - and should be used wherever possible.
So, what sort of trouble are you having? What works? What has failed? How do you wish to use RW? Is it failing to publish as expected? Have you read all the docs and pages on common troubleshooting?