Simple installation:

    make
    make install

If you have multiple versions installed, set the environment variable
PG_CONFIG to the pg_config program that corresponds to the
installation.  For example, in a Debian setup:

    make PG_CONFIG=/usr/lib/postgresql/8.4/bin/pg_config
    make install PG_CONFIG=/usr/lib/postgresql/8.4/bin/pg_config

To run the test suite, use make installcheck.