Oh shame on us... we don't really have a Get Involved page. Of course we'd like you to get involved into our project, but we just didn't have the time yet to explain how.
As it happens, the ways to get involved into an open source project are basically the same for all projects. Please have a look at the Incubator Guide To Participation. It's terse, but has pointers to additional information elsewhere at Apache. The sections on participating as a User and as a Developer apply here, too.