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:
Edit the font's layout to define the glyphs. Don't forget to update the metadata in the "COMMENT" cell. The metadata helps the PCell to compute properties of the font.
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.