Find this file in your flutter application => pubspec.yaml
Use local dependency
dependencies: flutter: sdk: flutter my_new_package: path: ./my_new_package
./my_new_package above means that the
my_new_package directory containing the
pubspec.yaml for the package is a sub-directory of the app.
If you have the package as a directory at the same level as the app, in other words one level higher up in the directory tree, you can use
../my_new_package (note the double dot) or a full path to the package directory.