Publishing a package is the last step to make it available to the Flutter community. All the publication is done by the pub tool. The command to make the publication is as follows:
flutter packages pub publish --dry-run
The --dry-run argument works like a pre-publication step, where the pub tool will make a validation process but does not actually upload the package. After everything is good, we can remove the --dry-run part:
flutter packages pub publish
This will effectively publish the package to the pub site so that every source code is published to the pub repository. Only hidden files and ignored ones (in case of using Git) are not uploaded.
You can see more about the publish command here: https://www.dartlang.org/tools/pub/publishing.