- Find a green "B" on a Win opt line (meaning that a build has succeeded for a Windows Optimized build), click on it, a panel appears at the bottom
- On the bottom left of the page, you can see a link named "go to build directory". Click on it, that sends you to the location where the CI stores the build
- In the list, there is an installer executable, that you can use to install this particular Firefox build (for examples: "firefox-20.0a1.en-US.win32.installer.exe").
Please keep in mind this is very much a work in progress, and it is likely to break horribly, maybe destroying your computer in the process (you never know :D). No warranties, blah blah blah. If you find bugs, it would be much appreciated to have them filed on bugzila.mozilla.org.