Added some details to the celery4 readme.
# cosmic_ray_celery4_executor
Cosmic Ray execution engine that distributes execution via Celery 4.
+
+To use this, first install this plugin into your environment::
+
+ python setup.py install
+
+or::
+
+ pip install .
+
+Then start your worker::
+
+ celery -A cosmic_ray_celery4_engine.worker worker --loglevel=INFO
+
+Note that if you are using the "copy" cloning method, then you need to start the worker in the directory where you want
+it to execute.
+
+Then you need to specify "celery4" as your `cosmic-ray.execution-engine.name` in your configuration.
+
+After that, everything should work! For more details/inspiration, see the Cosmic Ray
+end-to-end test suite.
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