Bob, no picture, but here are the details:
On the 4-way shut off valve, one side has two inlets, and the other has two outlets. One of the two inlets if you try to blow through it is hard to blow through, the other you can blow through freely. For the one that is hard to blow through, this is the connnection for the water line in. You simply plumb this side of the 4-way shut off valve in line on the line in for the RO unit. The other side of the 4-way, the side you can blow through freely, you plumb in line the product water coming from the RO unit.
It can be confusing, so read and re-read...