Right click on Sins within Impulse and choose the archive option. After it has finished, to easily find the directory where archives are stored (which differs somewhat between XP and Vista, but is under Impulse's folder in Application Data in All Users), go to the blue orb in the upper left hand corner, click restore archive, and Explore the folder that it lands you in (you'll probably need to go up one level to do this).
As a note, if you want to run 1.12 alongside Entrenchment, for the duration of the beta, you'll need to copy the Sins program directory to a different location before installing Entrenchment. This should be addressed by launch.
