[Asking] how to change and add Additional buff skill stats

[Ecrypter]

Hi epvpers limme know how to change and add additional buff skills?

Example in Crackshooter job
Skills Bow Mastery i want to change the Increased attack power (Bow) + 20 into a higher amount and adding extra effects like increased attack +45% or more.?

Thanks n advance, more power epvpers