If you want to continue work on a plugin which already exists in a repository, you can pull it into your environment by cloning it from the repository.

Make sure to install your composer dependencies and update your database after pulling the repo.

The following is an example of how to continue work on the mwp-rules plugin.

$ git clone https://github.com/codefarma/mwp-rules
$ cd mwp-rules
$ composer install
$ wp plugin activate mwp-rules
$ wp mwp update-database mwp-rules