Press TAB key to bring up the console when you run your game via the Visionaire Studio editor. Type print log to display the log file contents in the console window.
David recently added a debugging tool for Lua scripts to VS, but I've not tried using it yet, nor do I know if he implemented it directly into VS yet or whether you still need to use a third party application.
I myself write my scripts in an application called Sublime Text 3. As for debugging, if something doesn't work then I check the log files generated by VS to see which line(s) are causing offense & the reason / warning why, then I fix my scripts based on that, mostly by trial & error.
I recommend getting to grips with the editor & action parts themselves first, before you try to get to grips with scripting, as most things can be done without scripting. If you do happen to have a background in scripting / programming & find it more comfortable than the visual design approach, then by all means, delve into the scripting side of things as you please.