he is suggesting you use the "target" switch so that you make sure you are sending the rebuilt rpm to your source directory. your switch's need to have -- instead of - which will send it to rpmbuild.
edit- your problem was getting the commands wrong(they where almost correct both times but almost is not good enough
you need to do
rpmbuild --rebuild filename.src.rpm
then watch for a line that starts with something like
"wrote to /usr/src/RPM/RPMS/i686/filename.rpm" and cd to that directory and then do
rpm -ivh filename.rpm using your preferred command needed for rpm.
hope all that makes since.