The goal is to request a page from wechall but using the URL given in the challenge description instead. Depending on your setup, you might be able to achieve this in a few different ways.
Some suggestions on good things to look up:
* How URLs work (what is a URL? what is a host?)
* How the Domain Name System works
* How the HTTP protocol works with regard to hosts
* How to mess with the above on your specific operating system
And remember that even if something doesn't directly read to a solution, if you're learning things, you're doing just the right thing