By describing your actions, i meant on how you installed the theme in the first place
But nonetheless, it is correct to put the archive file in the ~/src/rpm/SOURCES
in what format is the archive? .zip, .tar.gz? PCLOS standard is to use .xz, so if you are using pkgutils-thunar, when you right click on the archive you'll see the option "convert to .xz".
Next step is to create .spec file. Since there are a lot of gtk themes already packaged, we can use some other similar package's .spec file.
As soon as i finish some work on zen-mini-finall, i'll continue to the next step