Your new package is there! You can edit the package properties in the package manager. Use the edit button in the upper right corner of the package details panel to open the package editor.
Here is what you should do:
The Python library is a standalone, native library. It can be used through "import" from other Python code. It is not embedded into KLayout's macro framework, so you have to edit it with your favorite text editor. Python will look for files in the "python" subfolder of the package.
In the package details you will find the local path to your package data under "Installation". You can use any versioning system to manage your files there.
Once you have finished your package, don't forget to specify the package version so users of you package will be informed of updates. Finally you can publish the package files to a place of your choice and submit the download URL to the Salt Mine server.