Before you add insulation, consider air sealing your attic, meaning use a closed cell foam to seal penetrations in ceiling such as top plates, holes for electrical, lighting and plumbing. This will prevent air communication between the attic and the conditioned space something that just adding blown in insulation cannot do. If you are experiencing comfort issues in your home, are looking for energy saving or health benefits reach out to home performance professionals and have a blower door test preformed to determine the amount of air leakage your home has and get the best solution. If you're interested in this take a look at Corbett Lunsford and his youtube channel Home Performance.
But to answer your question build a wall around your attic access to prevent the blown in insulation from falling through, put a seal on the attic access frame (kinda like a door seal) and adhere bats of insulation to the door itself.
Here is a link for some air sealing tips. https://www.energyvanguard.com/blog/56102/The-3-Rules-of-Air-Sealing
And here is one for why it's important http://energysmartohio.com/how_it_works/air-sealing/