The documentation on how to run it is in the readme. They've only got pre-release builds available on their website, since the tech isn't production ready yet.

I've been compiling it locally and playing with it. I run it like:

$ servo https://news.ycombinator.com

To do that, I've got an alias set up to point to my dev build.

alias servo='f() { /home/tychi/SourceCode/servo/mach run --release $1 };f'