Add documentation for setting/removing admins (#218)

services/admin-service/README.md

@@ -28,7 +28,47 @@ This will read in a file named `.env` for environment variables. Therefore, your
 FIREBASE_SERVICE_ACCOUNT
 ```
 
-This corresponds to the service account for the project on Firebase itself.
+This corresponds to the service account for the project's development environment on Firebase itself. 
+
+## How to add/remove admin rights for users on the application
+
+1. Run the command below. This will start up the admin service locally:
+```shell
+dotenv -e <insert full path of env file> -c development -- yarn dev
+```
+
+Although the command is `dev`, the Firebase admin rights can also be added to/removed from the users on the production
+or development version of the application. This is because the users and roles are stored remotely on Firebase.
+
+The application version affected depends on the value of 
+the `FIREBASE_SERVICE_ACCOUNT` environment variable in `<insert full path of env file>`.
+
+Hence, if your `FIREBASE_SERVICE_ACCOUNT` environment variable has the service account for the production application,
+the admin rights will be added to users registered in the production app.
+
+1. To set admin rights on a user, make a `PUT` request with `uid` corresponding to the user's uid in the Firebase project
+corresponding to the application version. You can do this using a tool like [Postman](https://www.postman.com/), 
+which you need to install separately.
+
+```
+http://localhost:5005/api/admin-service/setAdmin/<uid>
+```
+
+![Set Admin Example](./setAdminExample.png)
+
+1. To remove admin rights from the same user, make a `PUT` request with the same `uid`.
+```
+http://localhost:5005/api/admin-service/removeAdmin/<uid>
+```
+
+### Shortcut
+
+If you are setting/removing admin rights for users on the dev environment, you can simply run:
+```shell
+yarn workspace admin-service dev:local
+```
+
+This uses the default `.env` file which has a `FIREBASE_SERVICE_ACCOUNT` corresponding to the development app.
 
 ## How to do automated testing
 Automated testing is done using a [Firebase Local Emulator Suite](https://firebase.google.com/docs/emulator-suite).