I have had a few questions lately from people who want to make my travel duffle sewing pattern and they have never quilted. The quilt for the duffle consists of three layers. The bottom layer will become the lining of your bag, I use kona cotton muslin. You will need a large craft table to layout the fabric. You will be using pins, so you don't want to scratch your dining table.
First you press the muslin so you do not have any creases, and you lay it out flat on your work surface. Some people even tape the edges down to keep from getting even the smallest pucker in their quilt back.
Second, put the batting on top of the muslin.
Third, lay your feature fabric on top of the batting.
Fourth, pin the three layers together with safety pins about every 6" apart.
Here is a video showing the pinning process and a really great tool I am going to have to get myself!
The reason you use safety pins: Getting a large piece of fabric quilted on your home machine will require rolling it up from the right side as it gets to be too much to fit through the arm of the machine. If you use straight pins, you will get stuck by them even if you are careful.
After your fabric layers are pinned, you run the fabric through your machine, using a walking foot. I don't quilt them much for the duffles. I just run 4 wavy lines down the length of the fabric. I have seen beautiful duffles made from my pattern with more detailed quilting on them. If you want to take more time with the quilting part, you certainly can stitch more.
I hope this helps!