To use a sluice pan, place it parallel to the flow of water in a swiftly flowing stream with the riffles upward and at a depth where you can see water cresting as it flows over the riffles. Slowly feed gravel into the head of the sluice box. As the gravel washes down, any gold it contained will be captured behind the riffles.
A sluice works to separate gold from gravel because gold is denser than gravel and therefore settles out of moving water faster than gravel.
Setting up a sluice in a stream so that it captures the maximum amount of gold is complicated, says Where Gold Is, because proper placement of a sluice involves a number of variables, including the water's velocity and depth, the sluice's incline and how quickly one feeds gravel into the head of the sluice. To assist gold prospecting novices, Where Gold Is has posted videos demonstrating how to set up and use a sluice. As of 2015, these videos can be accessed at WhereGoldIs.com.
Another resource for learning the details about using a sluice is a monograph published by Keene Engineering entitled "Sluicing for Gold 101." This monograph is available under the Resources tab at KeeneEng.com.