add install instructions

docs/usage.rst

@@ -3,5 +3,27 @@ Usage Guide
 
 To use this code, please clone it onto your local machine: ::
 
-    $ https://github.com/ARCTraining/swd3-demo.git
+    $ git clone https://github.com/ARCTraining/swd3-demo.git
+    $ cd swd3-demo
 
+Install Hypot
+-------------
+
+To install the hypot package into the environment using `setup.py`, use: ::
+
+    $ python setup.py install
+
+Using the functions
+-----------------
+
+If you want to create a personalised script, you
+can import the hypot modules as follows: ::
+
+    from hypot.calc import squared, addition, sqroot
+
+Uninstall Hypot
+---------------
+
+To remove hypot: ::
+
+    $ pip uninstall hypot