The VA Help Document is found in the root directory of your VA installation. You can also right-click on the top of the main VA user interface and select 'Help Document.' As a new user I strongly encourage you to read through the manual. Yes it's long, but Gary does a good job keeping things light with his humor.
The native time-based functionality of VA is often sufficient for most people, though perhaps you have some mission-critical stuff that you really need to run through the scheduler. Here is a small example for the time-based output you're looking for using the native VA functionality:
// Store the current hour (based on 24 hour clock) in an integer variable
Set integer [~~CurrentHour] value to the converted value of {TIMEHOUR24}
// Check if current hour is between 12am-11am
Begin Integer Compare : [~~CurrentHour] Is Less Than Or Equals 11
// Say something with text-to-speech
Say, 'good morning' (and wait until it completes)
// Check if current hour is between 12pm-5pm
Else If : ([~~CurrentHour] Is Greater Than Or Equals 12 AND [~~CurrentHour] Is Less Than Or Equals 17)
// Say something with text-to-speech
Say, 'good afternoon' (and wait until it completes)
// Otherwise...
Else
// Say something with text-to-speech
Say, 'good evening' (and wait until it completes)
End Condition
// Say something with text-to-speech
Say, 'The time is {time}.' (and wait until it completes)
Note that you can't just copy-paste the above directly into VA. You'll need to generate the actions yourself using the above as a roadmap. Also note that the above actions use the tokens {TIMEHOUR24} and {time}, which you can read about in the manual.