First of all you need to be a bona fide freelance contractor working for yourself on a contract by contract basis. You also need a set of skills that other people need and are willing to pay for - unless you do work for free - (in which case HRI has some projects for you!)
You will then need to let HRI and those doing projects know that you are available - under whatever terms you care to name. There really isn't any limit on what skills are needed - the terms "technical resource" and "business resource" cover a lot of ground.
HRI is a web-based collaborative project site where most of the work is accomplished over the Internet. To work this way there are some basic requirements which make this productive. (It is not impossible to work with less - just really slow and awkward.)
- Broadband - fast enough for HD video. (Most of the tutorials are HD video so that the user can actually read the screenshots.)
- dual screens - one for you and one for everybody else. (Sometimes there's a lot more listening than talking - and if you're talking - hopefully, other people are listening)
- a Google username - HRI is currently built on Google sites and Documents
- a willingness to work within the HRI framework - which for the most part is Google docs and sites. (free - did we mention that - free....). Once your project matures you may wish to move to a more expensive collaborative platform (AutoDesk 360 comes to mind).