adding TPR installation instructions to the walk-through

Fixes #598

docs/walkthrough.md

@@ -38,15 +38,43 @@ The service catalog is packaged as a Helm chart located in the
 [charts/catalog](../charts/catalog) directory in this repository, and supports a
 wide variety of customizations which are detailed in that directory's
 [README.md](https://github.com/kubernetes-incubator/service-catalog/blob/master/charts/catalog/README.md).
-To install the service catalog system with sensible defaults:
+
+### The Service Catalog Database
+
+We'll be interacting with a variety of resources in the following steps. The service catalog API
+server needs to store all of these resources in a database. The database implementation in the API
+server is pluggable, and we currently support the following implementations:
+
+1. Etcd 3
+2. Third Party Resources (also, known as TPRs) - this is an _alpha_ feature right now. It has known issues
+
+The first implementation requires that the API server has access to an Etcd 3 cluster, and the
+second only requires access to the Kubernetes API to store TPRs.
+
+Even if you store data in TPRs, you should still access data via the service catalog API. It is 
+possible to access data via the TPRs directly, but we don't recommend it.
+
+### Install
+
+To install the service catalog system with Etcd 3 as the backing database:
 
 ```console
 helm install charts/catalog --name catalog --namespace catalog
 ```
 
-**Note**: Authentication and authorization are disabled in the Helm chart
-by default, even on the "secure" endpoint.  To enable them, set the
-`apiserver.auth.enabled` option on the Helm chart:
+To install the service catalog system with TPRs as the backing database:
+
+```console
+helm install charts/catalog --name catalog --namespace catalog --set apiserver.storage.type=tpr apiserver.storage.tpr.globalNamespace=catalog
+```
+
+Regardless of which database implementation you choose, the remainder of the steps in this
+walkthrough will stay the same.
+
+### API Server Authentication and Authorization
+
+Authentication and authorization are disabled in the Helm chart by default. To enable them, 
+set the `apiserver.auth.enabled` option on the Helm chart:
 
 ```console
 helm install charts/catalog --name catalog --namespace catalog --set apiserver.auth.enabled=true
@@ -55,8 +83,11 @@ helm install charts/catalog --name catalog --namespace catalog --set apiserver.a
 For more information about certificate setup, see the [documentation on
 authentication and authorization](./auth.md).
 
-**Note:** In the event you need to start the walkthrough over, the easiest way
-is to execute `helm delete --purge catalog`.
+
+### Do Overs
+
+If you make a mistake somewhere along the way in this walk-through and want to start over,
+check out the "Cleaning Up" section below. Follow those instructions before you start over.
 
 ## Step 2 - Understanding Service Catalog Components