Looking to Create New Battle Ability, activated by Campaign Skills

[Versidia]

So, I'm looking to create a new battle ability, activated by expending a character skill in the campaign. It looks like I'll need to make a script for it work like this, but I'm not sure where to start with this - everything I've done so far has been with databases. How do I set up a script for enabling abilities?

[Versidia]

To clarify, my problem is that I don't know how to even open the game's scripts, let alone edit or create them. Guides for previous TW titles refer to things not in my Steam installations, and I can't find a TW:WH scripting guide.