Unpack the package with tar xzvf grafist-x.x.x.tar.gz
Change to grafist-x.x.x directory and type ./install.sh
Grafist-installer has a consol based menu that one can change "path to webserver", "ethernet interface" and other options.
You must have installed the apache, php, and gd packages to successfully install Grafist.
If your system supports rpm, you may select "Build an RPM package with your choices" option. In this case, installer builds an rpm package; grafist-x.y.z-1.i386.rpm.
Running rpm -i grafist-x.y.z-1.i386.rpm will install grafist.
If you use Slackware, you may select "Build a Slackware (.tgz) package with your choices" option. In this case, installer builds a Slackware package; grafist-x.y.z-i386-1.tgz.
Running installpkg grafist-x.y.z-i386-1.tgz will install grafist.
Otherwise installer will configures the source, runs make, and make install.
Remember you need superuser rights to do so.