This is something you would use an Adjustment for.
Adjustments can be used to modify various things on a creature... AC, attacks, damage, skills, etc.
On the "Adjust" tab, look under "Other Adjustments" and you will find a variety of Adjustments that adjust skills.. one skill, all skills, all skills with the same ability modifier, and so on.
For these, you would need to add three single-skill adjustments, one for each of the skills. I think the bonus is a Trait bonus, specifically, so you would use the typed bonus adjustment to add it... that's because if you have another Trait that also gives a bonus to the same skill, the bonuses overlap and do not stack. Check the wording on the trait to make sure, though.
EDIT: As soon as I posted, I noticed that some of the Adjustments are not in the core, but are in the Community Pack (ShadowChemosh's Adjustments source). They're really very useful.