Steven's Park trail can be found at the end of the park. The park is small; just walk straight through it.
The trail roughly follows the creek, which in rainy months could provide you with an obstacle, possibly even an impassable obstacle.
After around 1/4 mile you may find a fork in the path. Take the fork that crosses the creek. The way that heads to the right will only take you up to the street.
At approximately 1/2 mile you should come to a concrete structure which is a debris dam. You may have encountered some other small forks in the trail before reaching this. There is one spot in particular where there is a low hanging large oak tree. The debris dam is shortly past this tree.
Last time I was there someone had built some kind of lean-to out of corrugated tin and old boards. You can see this structure (if itŐs still there) from the debris dam.
As dry as Santa Barbara gets it is surprising to see this debris dam protecting the city from this small creek, but when there is a good and heavy rain all sorts of trees, boulders, mud and torrents of water can threaten the houses below. That's why it's there.
The trail continues toward the direction of the lean-to (or toward the mountains if it's not there anymore.)
Around approximately 3/4 miles, after you pass a curious drainage structure peering from the hillside on your right, there should be a very prominent fork in the trail. This is the junction with the Jesusita Trail. If you turn right, you will be heading up a small hill toward the trailhead where people park their cars. You can go that way, cross the road when you reach the parking area, and take a look at the reservoir. Then, to complete this short hike, turn back and return the same way.
At the junction with Jesusita trail, should you instead choose to turn left, you can make a challenging day of it and choose to hike up to Inspiration Pt. or Arroyo Burro Trail, which are both described here