The entrance to Zion's "Subway" doesn't require a token or ticket, but it does require a permit. Information on obtaining a Subway permit can be found here. The Left Fork Trailhead is located on the east side of the highway about 8 miles north on the road from Virgin Utah to Kolob Reservoir. For photographers, the normal way to visit the Subway is from the bottom up. The top down route requires technical canyoneering skills and gear.
From the Left Fork Trailhead a well-maintained trail starts off level as it makes its way to a terrace overlooking the Left Fork. It then makes a fairly steep 400-ft drop, zigzagging down a gully to the streambed. Once you reach the stream, make note of the trail entry point, you don't want to miss the exit on the way back! Take a GPS reading here if you have one.
The route then follows the Left Fork streambed up the canyon. As you hike, you alternate between sections of hiker made trails, boulder hopping, and hiking right in the stream course. As there is no definitive route, some of the trails are of questionable value. In about two miles, the canyon starts to get more interesting and the streambed turns almost entirely to solid slickrock. You should not have to get in water more than ankle deep if you pick your way carefully.
In about 4 miles, you get to Arch Angel Falls. In my opinion this is the prettiest falls in all of Utah. The light here can be amazing in mid to late morning.