To install carthage, run the following command in macOS terminal (Applications->Utilities->Terminal)
sudo port install carthage
To see what files were installed by carthage, run:
port contents carthage
To later upgrade carthage, run:
sudo port selfupdate && sudo port upgrade carthage
Reporting an issue on MacPorts Trac
The MacPorts Project uses a system called Trac to file tickets to report bugs and enhancement requests.
Though anyone may search Trac for tickets, you must have a GitHub account in order to login to Trac to create tickets.