To FTP on you localhost you will need to setup a FTP Server, try the FileZilla server, available here. Here’s how to set it up
Then your FTP address will be “localhost” with the user & pass that you setup in the server, you can also assign the default folder.
I don’t use “local by Flywheel” but these are the steps for regular localhosts such as XAMPP & UwAmp, it should be the same.
I think you misread my question – I am using Local by Flywheel NOT Flywheel (yet) as a host.
This isn’t a WordPress question; it is best handled by Flywheel support.
I also don’t understand why you need FTP server software since “local” means the files are on your local system. It’s certainly not needed for WAMP/XAMPP/MAMP/etc…
There is no FTP on localhost. Just open the folder.