Thanks for posting the request!
The import/export feature is not implemented yet. It is on the planned features list.
At the moment you can manually copy the freeter data directory from one machine to another. Freeter stores its data in <AppData>/freeter2/freeter-data directory, where <AppData> is one of these depending on the operating system:
%APPDATA% on Windows
$XDG_CONFIG_HOME or ~/.config on Linux
~/Library/Application Support on macOS