Look, this is not a feature which is supported by 3rd parties.
If you need to install AirBags (AB), you must have a car which has any AB version.
Use required stuff to make it operational and there you go...
Following is the minimum requirement for installing AB in a car which support it.
1-Shock Sensors
2-AB enabled Steering Wheel.
3-AB enabled Dash (if Dash AB is required too)
4-Wiring
5-Certified and Qualified technician to install it.
Note: AB cannot be tested, because, you can't do a crash test on your vehicle, hence you never know weather you've installed them successfully or not.
Best way is to use seat belts, that saves lifes, but air bags only prevents debres of WindScreen from hitting you.
if you still insist, go ahead and visit URL below
http://www.autowoods.com/installation_guide.htm
Regards,
Dr.MAQ