Pull updates from source repository

I have a repository on Github that is a fork of another repository. I made some changes, and they were pulled into the original repository, and more changes have been made there since then.

My forked repository is now out of date, and I want to make some more changes to it. Nothing has happened in my repository sin开发者_C百科ce the changes were pulled into the original, so it just needs to get all the new changes. How can I do that?

It is explained here: http://help.github.com/forking/