Makefile.global is included in all of the sub-makefiles of aolserver. Usually you edit include/Makefile.global for any of your system-specifc configurations and then type make in aolserver top-level directory. It sounds like you have a binary distro. For a source distro your top-level directory will look something like this:
1016 nsadmin@localhost:/usr/local/aolserver/aolserver3_1 >ls ChangeLog LICENSE.txt doc nscgi nsext nspd nssha1 nsvhr scripts tcl8.3.2 DISTRIBUTION.patch Makefile encoding-doc.html nscp nslog nsperm nssock oracle-driver-2.3 tcl thread DISTRIBUTION.txt README.txt include nsd nsodbc nsrewrite nsunix oracle-driver-2.3.tar.gz tcl7.6 win32 1017 nsadmin@localhost:/usr/local/aolserver/aolserver3_1 >
Typing "make install" in this directory should build and install aolserver in whatever directory is specified as the "INSTALL" directory in Makefile.global.