Start out by looking at your AppEngine application you have created. There will be a lot of logs if you have a site you are running with a lot of traffic. At some point you want to do some analysis of what’s going on. A post on the google developer blog [http://googleappengine.blogspot.com/2012/07/analyzing-your-google-app-engine-logs.html] gives some insight into how to go about it. The post points you at slides in http://log2bq-codelab-io12.appspot.com/slides#2 which explain how to import the AppEngine logs into BigQuery. There are a lot of steps.
You can set up log export via the Log Export Panel into Big Table. https://cloud.google.com/logging/docs/export/configure_export#ways_to_configure_logs_export shows you how to do it.