I am following the book Introduction to Programming with Xojo page 146 in the PDF numbering scheme.
Cannot see where to access the Window’s Open Event -
where can I see this as per top of page instructions.
See my screen capture to find out what I did:
https://vimeo.com/138408869
Link is not valid…
Select the Window in the Navigator and add an Event (f.e. by Right Clicking) and add the Open Event. 
Adding an event handler to a control / window is covered earlier in the book. Perhaps you missed it.
It’s such a shame that events have to be manually added, it was so much simpler when they were always available. In my experience this seems to be a common issue with new users.
@Kim Kohen: Agreed. It is my biggest gripe with the Xojo IDE.
Open the item once, add every event once, done
For web apps having it present but empty is quite different than not present at all
Having all events at once as it was in RB could be source of confusion as well. I find adding only the ones I need much cleaner, showing at a glance which events are actually implemented.
Hows that saying go again … different strokes for different folks 
The old system had its issues as well.
Having them all show caused a lot of clutter with all the empty events that were mostly never implemented.
So a means to hide unimplemented events was added to allow users to hide unimplemented ones and reduce the clutter.
Then you had to remember that you had set that on IF you wanted to implement one that you could not see any more (not much different than having to add it now).
I’m not convinced either is vastly superior to the other.
I’m sure there will be lots of debate about this
You could do that in the old IDE too. Show/Hide empty.
So still a negative in the new IDE.
Speaking as someone who is not using the web edition: What is the difference?
present means its implemented - although the implementation does nothing
present means its not
no code in the item ? not implemented
and this affects what events get transmitted between the front end and back end
Its like the difference between a column in a database that is NULL or one that contains “”
a NULL column is “no value has ever been assigned”
a column with a value of “” HAS a value its just an empty string
It would be less of an issue if objects reliably asked for events to be added. I set up a report the other day and double clicking a report object in the navigator didn’t open the ‘add an event’ sheet. I had to use a contextual menu which is not an issue, but it’s also not consistent with the rest of the IDE. I was aware there were report object events but a new user wouldn’t know and would just assume there were none.
I’m working on a feedback for this and a couple of other report bugs…