Install docker. Use the Get Started button at the top of the page, which autodetects your OS and presents the appropriate instructions.
Build for all stacks:
$ make build
Build for a specific stack:
$ make build-$STACK
heroku plugins:install https://github.com/heroku/heroku-buildpacks
cd heroku-buildpack-pgbouncer
git checkout master
heroku buildpacks:publish heroku/pgbouncer