If you installed in the default location, this file should end up at
/usr/local/include/link-grammer/api.h
and so #include <link-grammer/api.h> should find it.
It is possible, but unlikely, that you need to say gcc
-I/usr/local/include when
compiling ...
--linas
--
"I like to pay taxes. With them, I buy civilization." -- Oliver Wendell Holmes