You can get Wren:IG Web Application Archive (WAR) in couple of ways:
The easiest way to get the Wren:IG is to download the latest binary release.
You can also run Wren:IG in a Docker container. Official Wren:IG Docker images can be found on Docker Hub.
You can also create your own build from the source code. Manual how to build the source code can be found here.