I am a self taught sewer, so I apologize in advance because I do not know a lot of the proper terminology for a lot of stuff. Hang in there, I'll explain things to the best of my ability and use lots of pictures.
For this purse, I used a really basic pattern (because it is fast), that you can find here. I recommend that you read through the tutorial a few times, and maybe make a bag or two without a zipper if you haven't made one like this before because I won't be going into the "how to" of making the actual bag. I'm just going to detail how to get the zipper into it. I also think this method will work with a gusseted bag with a few modifications.
Here is a picture of the finished purse so you can get an idea of how it will look when you are all done. I prefer to have my zipper about an inch down into the bag lining because that way it doesn't bubble up the way it does when you put the zipper right on top.
Step 1: Step #1 - Zipper Length and Taking It Apart
Ignore the ruler. It is just holding the zipper down flat.
At this point, you can take the zipper apart. Don't lose any pieces (like I did). You should put the zipper pull and the little metal u-clip from the bottom of the zipper in a safe place.
Cut out the pieces for your purse as per the original Jordy Tutorial.
Step 2: Step #2 - Preparing a Casing for the Zipper (or Hiding the Ugly Bits)
The 2.5 inch widths will end up giving you a 1.5 inch opening with the zipper closed at the top of your purse when all is said and done.
Next, you will need to fold one of your strips in half the long way (good side out) and iron it. (Third picture)
Now open it up and fold the outside edge to the middle crease that you just made. Iron it. (Fourth picture)
Fold the other side in toward the middle crease as well, and iron. (Fifth picture)
If you were to open it up at this point, the strip would be creased into 4 equal sections.
Fold the strip in half lengthwise where the two edges meet in the middle and iron. (Sixth picture)
This will be the casing for one side of the zipper. now repeat all of those steps with the other strip.
Step 3: Step #3 - Sewing the Zipper Into the Casing
Take one piece of your casing and half of the zipper. Open the casing.
Determine which is the underside of the zipper. Lay the zipper so that the underside faces up and place the opened casing on top with the inside of the casing facing down toward the zipper. Pin in place so that the teeth are showing along the top. Make sure the zipper is centered lengthwise. (Picture one and two)
Put you zipper foot on your sewing machine and with the material side down, sew the zipper to the casing. (picture three)
See how the zipper is sewn on? (picture four)
Now fold the other half of the casing over top of the zipper. Pin it if you want. (picture five)
With your zipper foot, sew the zipper and casing together. (picture six)
You should have a seam like in picture seven when you are done.
Phew. Now do the same with the other half of the zipper.
If all that seems a bit complicated, you could sew a piece of 1 inch gros grain ribbon onto each side of the zipper instead of making a casing. This will cover the zipper in the same way, but takes way fewer steps. I have to warn you though, that it is not nearly as strong. Here is a pic of one that I made using ribbon instead of the casing. (picture eight)
Step 4: Step #4 - Sewing the Zipper to the Lining
With your regular foot, sew the casing down to the lining. Make the seam as close to the non-zipper side of the casing as you can. (picture two)
When you are done sewing all the way across, it should sort of look like a hinge! (picture three)
Do the same with the other zipper/casing and lining.
At this point, I like to slide the zipper pull on and take the zipper for a test drive to make sure that everything is going to line up ok. Once I'm sure, I take the pull off again. (picture four)
Step 5: Step #5 - Almost Done!
Finish sewing the rest of the purse together as per the purse tutorial for the Jordy Bag.
Step 6: Step #6 - Finally!!
Success at last! Now put the metal U-clip thing that stops the zipper back onto the end. (picture two)
Pictures three and four show the zipper open and closed.
I hope this has been helpful! If you have any questions, let me know and I'll try to clarify. Happy Sewing!