Merge pull request #53 from oracle/issue-49

update doc to mention the need to login to docker store and to accept…

Author: rjeberhard

site/installation.md

@@ -21,12 +21,15 @@ First run the build using this command:
 mvn clean install
 ```
 
-Then create the Docker image as follows:
+Then login to Docker Store so that you will be able to pull the base image, and create the Docker image as follows:
 
 ```
+docker login
 docker build -t weblogic-kubernetes-operator:developer --no-cache=true .
 ```
 
+Note: If you have not used the base image (`store/oracle/serverjre:8`) before you will need to visit the [Docker Store web interface](https://store.docker.com/images/oracle-serverjre-8) and accept the license agreement before Docker Store will give you permission to pull that image. 
+
 We recommend that you use a tag other than `latest` to make it easy to distinguish your image.  In the example above, the tag could be the GitHub ID of the developer.
 
 Next, upload your image to your Kubernetes server as follows: