The PostgreSQL 8.2.0 sources can be obtained by anonymous FTP from ftp://ftp.postgresql.org/pub/source/v8.2.0/postgresql-8.2.0.tar.gz. Other download options can be found on our website: http://www.postgresql.org/download/. After you have obtained the file, unpack it:
gunzip postgresql-8.2.0.tar.gz tar xf postgresql-8.2.0.tar
This will create a directory postgresql-8.2.0 under the current directory with the PostgreSQL sources. Change into that directory for the rest of the installation procedure.