Update README.md

README.md

 # UUS - Uncomplicated Url Shortener
 This is a url shortener written in python with flask
+
+## Management CLI
+
+A simple CLI is provided to add, modify and delete admin users. `REDIS_URL` must be provided unless it is the default. Also, `FLASK_APP=uus` must be set when not running in Docker (the Dockerfile already sets this).
+
+Run `flask` to get the list of commands.
+
+In the docker container you can run `uus` directly to get to the CLI, for example
+
+```
+$ docker exec -it uus_uus_1 uus adduser admin
+Password: 
+```
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