error when try to push from workspace into GitHub repository

When I trying to push my codes in workspace into GitHub, I get the error below. It's right after I typing my username and user password of GItHub. And i've researched around at Google, still get confused.

Thank you very much for helping:

treehouse:~/workspace/JavaScript$ git push --help
warning: failed to exec 'man': No such file or directory
fatal: no man viewer handled the request
treehouse:~/workspace/JavaScript$ git push -u origin master
Username for 'https://github.com': rachelxie1985
Password for 'https://rachelxie1985@github.com':
To https://github.com/rachelxie1985/JavaScriptBasics.git
! [rejected] master -> master (fetch first)
error: failed to push some refs to 'https://github.com/rachelxie1 985/JavaScriptBasics.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another reposit ory pushing
hint: to the same ref. You may want to first merge the remote cha nges (e.g.,
hint: 'git pull') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.