This is a Heroku buildpack for adding wget to your application.
More likely, you'll want to use it as part of a larger project, which needs to use wget. The easiest way to do this is with a multipack, where this is just one of the buildpacks you'll be working with.
$ cat .buildpacks git://github.com/heroku/heroku-buildpack-ruby.git git://github.com/johnbeynon/heroku-buildpack-wget.git $ heroku config:add BUILDPACK_URL=git://github.com/ddollar/heroku-buildpack-multi.git
This will bundle wget into your instance without impacting your existing system.
Copy the snippet above into CLI.