You'll want to make sure you check out the installation page for any sound library you've purchased from Sunday Sounds including Worship E. Pianos, Organs and Strings for Ableton Live. Worship Strings for Ableton requires the free "Labs Strings" VST/AU plugin from Spitfire Audio which is available here. You will not need to download a VST for the Organs or E. Pianos. We sampled those ourselves and the included sound content is within the Ableton files.
This installation video will guide you through the installation process for our Ableton Live sound libraries:
After you get it installed, you can learn how to use the sounds as presets in your preset library here: