How can I install citeref via tlmgr from TexLive 2012?

citeref.sty is available on CTAN as <CTAN>/macros/latex/contrib/citeref/citeref.sty; it's not on TeX Live because the file shows no licensing notice whatsoever, so a non free license must be assumed in order to comply with the guidelines on free software.

You can't use tlmgr for installing it; however it's easy to install it manually with the following shell commands

wget http://mirrors.ctan.org/macros/latex/contrib/citeref/citeref.sty
sudo mkdir -p /usr/local/texlive/texmf-local/tex/latex/citeref
sudo cp citeref.sty /usr/local/texlive/texmf-local/tex/latex/citeref
sudo mktexlsr

The first command can also be

curl -O http://mirrors.ctan.org/macros/latex/contrib/citeref/citeref.sty