Add documentation of API

README.md

 # imperial_doc_materials
 
-Python client for the [Materials API](https://api-materials.doc.ic.ac.uk/) in DoC
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+Python client for the [Materials API](https://api-materials.doc.ic.ac.uk/) in DoC.
+
+## Setup
+
+Add this code to your Flask's ```app.py``` if not done already (it should already be present in the Flask template):
+
+```python
+# Add integration to the Materials API
+import imperial_doc_materials
+imperial_doc_materials.init_app(app)
+imperial_doc_materials.set_redirect_url('auth.login')
+```
+
+## Using the Materials API in a Flask route
+
+Again, there are examples of this in the template. You must use the ```@using_materials``` decorator before the route function definition. This will give you access to a ```Materials``` client object which you can use to make requests.
+
+```python
+@home_blueprint.route('')
+@login_required     # Indicate that the user must be logged in (via LDAP)
+@using_materials    # Indicate that we want to access the Materials API
+def dashboard(materials_client, user):    
+    my_courses = materials_client.get_courses_for_year("2122")
+    return render_template('dashboard.html', user=user, my_courses=my_courses)
+```
+
+**Important:** if using other decorators such as ```@login_required``` provided by the [imperial_ldap package](https://gitlab.doc.ic.ac.uk/paas-packages/imperial_ldap), the parameters to the function appear in inverse order. For example, in the code above, the login decorator appears first, so the ```user``` parameter provided by it goes last.
+
+## The API
+
+### ```Materials``` class:
+
+- Creating a new client given a username and password:
+
+    ```client = Materials.create_client(username, password)```
+
+- Getting the list of enrolled ```Course```s given an academic year (of the form "2122"):
+
+    ```courses = client.get_courses_for_year(academic_year)```
+
+- Getting the list of all the ```Resource```s that are available for a given academic year:
+
+    ```resources = client.get_resources_for_year(academic_year)```
+
+### ```Course``` class:
+
+The available fields of a ```Course``` instance are:
+
+- ```title``` (string): the full name of the course
+- ```code``` (string): the code of the course
+- ```has_materials``` (bool): whether the course has any materials uploaded
+- ```resources``` (List[Resource]): a list of all the ```Resource```s for that course
+
+### ```Resource``` class:
+
+The available fields of a ```Resource``` instance are:
+
+- ```id``` (int): the internal DoC ID of the uploaded resource
+- ```title``` (string): the name of the resource
+- ```type``` (string): if the course is a "file" or a "link"
+- ```category``` (string): the category of the resource
+- ```url``` (string): the URL to the resource
+- ```course_code``` (string): the code of the corresponding course