Add section on Usage

README.md

@@ -19,6 +19,39 @@ Requires Python 3.7 or above
 pip install git+https://github.com/mberk/kelly.git
 ```
 
+## Usage
+
+```
+>>> kelly.calculate_kelly_stake?
+Signature:
+kelly.calculate_kelly_stake(
+    price,
+    is_back,
+    probability,
+    other_probabilities,
+    position,
+    other_positions,
+    bankroll,
+    kelly_fraction=1.0,
+    verbose=False,
+)
+Docstring:
+Calculate the optimal fractional Kelly stake when placing a single bet on an event that has one winner
+
+:param price: The price at which the bet is being placed
+:param is_back: Whether you are backing (True) or laying (False)
+:param probability: Your fair probability for the outcome you are betting on
+:param other_probabilities: A list of probabilities for the other possible outcomes. sum(other_probabilities) + probability should be equal to 1 subject to floating-point error but this is not yet enforced
+:param position: Your position - i.e. how much you are currently standing to win or lose - on the outcome you are betting on
+:param other_positions: A list of positions corresponding to the other possible outcomes. It is assumed there is a 1:1 correspondence between the elements of this list and other_probabilities
+:param bankroll: Your notional Kelly bankroll
+:param kelly_fraction: A fraction to multiply the optimal stake by. Defaults to 1
+:param verbose: Whether to generate log statements when numerically optimising the stake. Defaults to False
+
+:return: The optimal fractional Kelly stake
+Type:      builtin_function_or_method
+```
+
 ## Benchmarks
 
 Coming soon...