Don't do this.
If your app requires certain "default" defaults to operate, on first launch, notice they aren't there and write them out.
You are assuming too much about the installation: that the user doing the install is the primary user of the software; that only one user on the machine might be interested in using the software; that anyone is logged in at all!
Instead have your app set up its default environment on first launch. This will work for all users on the machine, including users created after your software is installed.