Houston is the particular WildStar Lua and form editor that comes with any WildStar installation to help with developing WildStar AddOns. It does not need some separate download. If you got WildStar installed, you have Houston already.
Some really good information and introduction can be found here:
- Graphical Form Designer for visual elements (windows, buttons...)
- (Weak but mostly up to date and complete) API Documentation (Helpfile with classes, evens and functions/methods available for addon development)
- Project Browser
- Generic IDE stuff like code indent, highlight and partial code-complete
- Loading sound files: http://www.readycheck.org/lui/guide_sounds.html
- This is an example for adding sounds to the Lui Aura addon, but the description can be used in order to create custom sounds for your addon