Clone your fork using the following command. If you have the mattermost-webapp environment set up or are planning on setting it up, you would typically clone your copy to $GOHOME/src/github.com/mattermost/mattermost-redux.
git clone https://github.com/<yourgithubusername>mattermost-redux
Run the tests to confirm everything is installed correctly. Doing this will also use npm to install any other required dependencies.
cd mattermost-redux
make test