ruby - heroku: command not found

this question has been posted befour, but the answers haven't worked. I should proberley mention that i am completely new to ruby. i incountered the error while doing a tutorial here are the steps: `[first_app (master)]$ gem install heroku` I get ``` Successfully installed heroku-2.24.0 ``` but when i try `[first_app (master)]$ heroku keys:add` I get ``` -bash: heroku: command not found ``` i then tried a bunch uninstalling the gem updating bundle reinstalling it but that hasn't helped ``` $ bundle exec heroku ``` `/Users/vng/.rbenv/versions/1.9.3-p125/lib/ruby/gems/1.9.1/gems/bundler-1.1.3/lib/bundler/rubygems_integration.rb:147:in` ``block in replace_gem': heroku is not part of the bundle. Add it to Gemfile. (Gem::LoadError) from /Users/vng/.rbenv/versions/1.9.3-p125/bin/heroku:18:in`'` ``` echo $PATH ``` `/Users/vng/.rbenv/shims:/Users/vng/.rbenv/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin` my gem environment RubyGems Environment: - RUBYGEMS VERSION: 1.8.11 - RUBY VERSION: 1.9.3 (2012-02-16 patchlevel 125) [x86_64-darwin11.3.0] - INSTALLATION DIRECTORY: /Users/vng/.rbenv/versions/1.9.3-p125/lib/ruby/gems/1.9.1 - RUBY EXECUTABLE: /Users/vng/.rbenv/versions/1.9.3-p125/bin/ruby - EXECUTABLE DIRECTORY: /Users/vng/.rbenv/versions/1.9.3-p125/bin - RUBYGEMS PLATFORMS: - ruby - x86_64-darwin-11 - GEM PATHS: - /Users/vng/.rbenv/versions/1.9.3-p125/lib/ruby/gems/1.9.1 - /Users/vng/.gem/ruby/1.9.1 - GEM CONFIGURATION: - :update_sources => true - :verbose => true - :benchmark => false - :backtrace => false - :bulk_threshold => 1000 - REMOTE SOURCES: - http://rubygems.org/ help is greatly appreciated