Access from Darwin to Jabiru is via the Arnhem Highway. This is a reasonable quality sealed road that is usually open all year round. Access from the south to Jabiru is via the Kakadu Highway, again usually open all year round. Check road conditions before setting off. It is around 3-4 hours drive from Darwin to Jabiru.
There is now an entry fee for Kakadu National Park - $25 per person over 16 years of age. The entry pass is valid for 14 days.
You can hire 2wd and 4wd cars in Darwin, with daily distance limits. Campervan rentals often don't have distance limits. A variety Coach and small group tours are also available from Darwin.
Some parts of the park are not accessible during the wet season, or are not accessible by 2wd vehicles during the wet season. Check road conditions and closures in advance.