Installing source rpm only extract the spec files and the tar.gz files inside /usr/src/redhat.
spec file is located inside /usr/src/redhat/SPEC and the tar.gz file is inside /usr/src/redhat/SOURCES.
spec is the file that you will use to set the binary configuration.
I will suggest to install a rpmbuild inside your home directory following this tutorial
so you won't have to touch /usr/src/redhat.