In order to compile and install KStars on your system, type the following in the base folder of the unpacked KStars distribution:

% ./configure --prefix=$KDEDIR
% make
% make install

Please do not forget the prefix argument to configure. If your KDEDIR variable is not set, set prefix to whatever folder KDE is installed in: this is usually either /usr, /opt/kde, or /opt/kde3. Also, make sure you do the last step as root.

KStars uses autoconf and automake, so you should not have trouble compiling it. Should you run into problems please report them to the KStars mailing list (kstars-devel AT kde.org).