how do i get entrenchment / diplomicy packs?

From Impulse they are a Direct Dowload product only.

http://www.impulsedriven.com/sinsdiplo

or buy trinity at the store, that works as well.

If you can find it cheap that works too. I don't see Trinity anymore in my area though and I assumed he had the base game though I doubt he's registered it since he's asking how to get the expansions. I'd have assumed he would have accidentally found the impulse store had he previously registered through impulse.