(limit of 4 images per post made me split this one up)
Repeat for the other openings.
7. Put in the seams.
Insert new rows of vertices and cut them to form 3 rows of new lines. Pull the center one in towards the middle of the model.
Pull the outter two lines together to where they are almost touching over the center line. Adjust the height of the outside lines if you have one side of the seam bulging out over the other. The closer you get the outter edges together, the harder the seam will appear. If you want it to look looser, just don't move the side lines quite so close together.
Repeat for the flat sections of the fabric.