To install (relies on jQuery):
Click on the X to open WadBug.
Home: details about the current device
Console: Console: A faux console where you can see log events and execute code. Click "help" to see some useful tricks, like using ":" for inspecting objects (eg :window.document).
Cache: cache manifest events (if any - will only show after a cache event has fired).
Live: won't make much sense to do here - it loads a file from the server and polls for changes via Ajax. As you can't update the change file, you'll only get some sample code (an alert that shows the date) executed once.
When you are developing with WadBug you can update the code and it will be automatically run on your phone, so you can do "live changes".