How to install pkg_add to archived freeBSD

ref:
https://www.garron.me/en/bits/change-pkg_add-source-ftp-version.html
http://ftp-archive.freebsd.org/pub/FreeBSD-Archive/old-releases/i386/6.3-RELEASE/packages/
https://www.cyberciti.biz/faq/howto-install-vim-text-editor-under-freebsd/

first, need to setenv packagesite to archived ftp url

setenv  PACKAGESITE http://ftp-archive.freebsd.org/pub/FreeBSD-Archive/old-releases/i386/6.3-RELEASE/packages/Latest

then install required package

# pkg_add -r -v vim-lite

done!