For starters, you need a pintuck presser foot and a double needle. These will be specific to your sewing machine. I use a 10ish year old Husqvarna Viking Easy Sew 350. My double needle is a Schmetz 2,0/80. When you buy your presser foot, the packaging will tell you what kind of double needle to buy. I believe that I have a 5 groove pintuck foot. There are many varieties. For my machine, the current prices for the feet are under $20 and the needles are about $4.00.
When you thread your machine, you need to have two spools of thread. My machine has an attachment that you can pop in place to hold the second spool. You then thread both threads together through the machine, down to the needle.
Then you thread one thread into one needle, and the other into the other needle. And, of course, you put on your pintuck presser foot.
Now you are ready to go. I am using purple fabric and white thread here for contrast in hopes that you will be able to see it ok. You would want to use matching thread if you were actually sewing on a garment or other project. If you go ahead and stitch one line you get a single pintuck as seen above. You will want to make sure that your pintuck is straight so you should either follow a guide along the edge of your fabric, or draw a line with chalk.
When you make your second pintuck, you can allow the first pintuck to ride in the groove in the presser foot to make sure that you have even spacing.
Two rows look like this. Then you can line up for a third and so on.
Sometimes I prefer to space them apart a bit, as demonstrated on the right side of the fabric above. To do that, I just followed a different groove in the presser foot.
Of course you don't need to make your pintucks in rows. The dress I made yesterday (see the post below) has a sort of radiating design. To do that, I marked the top and bottom of each pintuck with a pin. Starting at the top, I stitched from the top pin to the bottom pin. I have a pretty good eye for measurements and direction so I eyed this rather than drawing lines with chalk but that might be helpful.
Pintucks are often used at the top of a garment, near the neckline. They are also used in rows along the hemline. I made a tree top angel for our tree a number of years ago and used pintucks along the hem and it looks very attractive. I should also mention that pintucks work best in lightweight fabric.
I am working on another version of the pintuck baby dress and hope to have it up in the next couple of days!