First download the tar.bz2 or the rpm file from the official GnomeTV site gnometv.sourceforge.net. If you downloaded the RPM file you should type rpm -i gnometv-0.2-1mdk.rpm to install the package. It is made for Mandrake 6.1. If you downloaded the tarball file you should untar the package with bunzip2 -c gnometv-0.2.tar.bz2|tar xfv - then run ./configure --prefix=`gnome-config --prefix` --sysconfdir=`gnome-config --sysconfdir` and make, make install.
To use GnomeTV you can start it from a terminal window by typing gnometv, or you can add the GnomeTV applet to the panel by right clicking on the panel and selecting Add applet -> Multimedia -> GnomeTV.