The very small parking area at the park charges a fee for parking. Most folks opt to park just outside the park along the road... this may be necessary anyway; this is a very popular natural attraction. Once you've decided on where to leave the car, prepare to enjoy a very easy stroll through lush under/over growth. But, first stop and pay the entry fee! There is an odd automatic ticket machine right at the trailhead!
Next you'll start down the paved trail, complete with helpful handrails, only it might be better to avoid gripping the rails too tightly; they can be covered with small "worms"... adds a bit too much squish to the moment for most folks.
The setting is exceptional. I suggest looping counter clockwise (do not take the first left turn.) You will pass overviews of Kahuna Falls, then move on to enjoy the main attraction: the 420' Akaka Falls! This is a short but delightful hike.
The area adjacent to the park was once highly developed sugar cane fields. The cane still resides roadside. Chewing on those sweet, tough fibers can bring back memories... assuming you grew up in the South!
The short drive into the park is well worth the time and effort. Enjoy the lush setting, realizing that most of the plants you are looking at are not natural to the area, but seem to fit right in.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.