This is by no means the only way to go about rooting. There are other methods. This is what works for us. We have also rooted in water, plain perlite, and plain sand.
Start with a healthy cutting that has been dried for several days to weeks. Make sure any leaves are removed. Wet bottom of cutting and dip in rooting hormone. Mark the cutting with a marker about 4 inches from the bottom of the cutting. Mix 2 parts Perlite to 1 part Potting soil. Fill the pot with the soil mix, leaving 1 Inch from the top. Poke a hole in the soil with your finger. Sink the cutting into the pot until the marked line is even with the pot rim. Press the mix firmly around the cutting and add more if needed. Water it until water drains out the holes and place pot in a warm sunny spot. Do not water again until the soil is dry. When leaves start to appear, there should be roots. If you get resistance with a gentle tug, there are roots. When checking for roots, be very careful not to damage them. I like to use clear pots so I can see the roots. You can buy them from orchid supply shops, or use soda or water bottles (remember to poke lots of holes).