You can use the following commands:
gcloud preview docker -a
to update the local docker configuration with gcr.io credentials.
And then use the usual dockerCLI commands to click and drag images:
docker build -t gcr.io/<gcr_namespace>/<docker-image> .
docker push gcr.io/<gcr_namespace>/<docker-image>
Or for existing images:
docker tag <docker-image> gcr.io/<gcr_namespace>/<docker-image>
docker push gcr.io/<gcr_namespace>/<docker-image>
docker pull gcr.io/<gcr_namespace>/<docker-image>
CLI , , gcloud preview docker -a .