The STK software distribution is obtained by going to the STK home page, navigating to the download page, and downloading the latest ``source distribution'' (stk-4.5.0.tar.gz as of this writing). See the file INSTALL.md for instructions on installing it.
Note: On the CCRMA Linux systems, configure and make worked the first time. However, on a Mac with MacPorts installed, where some ports where using specific C and C++ compilers at the head of the search path (gcc and g++), it was necessary to configure like this:
./configure CXX=clang++ CC=clang