How to add "effective against armor"?

[Zwei-Gothic]

I'm trying to edit my dismounted gothic knights and forlorn hope so that they can stand a chance against other infantry by adding the "effective against armor" trait that they seem to be missing. Im not 100% sure that this would solve their problem of getting completely owned by infantry costing half as much as they do, but I figure its a start. The only thing they seem good at right now is killing peasants. How do I do this?

[Surgeon]

Change this line:
stat_pri_attr no
To this:
stat_pri_attr ap

In this case you need to delete the "no" because they don't have any other weapons attributes by default. If a unit already has some sort of attributes like "long_pikes" or something, just add "ap" to the list after a comma.