It doesn't look like you did a straight copy/paste from the docs, but just to be sure, your environment might not be set up correctly. If the repo you're forking is called testproject , your username is me and their username is they :
You should have forked and then cloned your repo. Your repo's address is ssh://git@github.com/me/testproject notice the ssh protocol
Then, you should have added they's repo as an upstream repo (that's the git remote add upstream). Github provides a link you can copy there, but you should use the git protocol if possible (see VonC's note about git, http and firewall). The command to add the upsteam repo is git remote add upstream git://github.com/they/testproject
Note that upstream is arbitrary. You can name it upstream or anything else you want. Also, make sure to get the /they and /testproject right as that will cause errors if the repo doesn't exist in that user's account