So you've bound off at the neck and you're almost done. Congratulations. There's not a lot left to do; graft the arm pits, put the neck/button band on, and sew down the hems. After that it's a quick wash and the jacket's done.
ARM PITS: These stitches have been on holders since you joined the body and arms of the jacket together. Just graft them, like the toe of a sock. I suggest using the 'lighter' color, and then going back through and duplicate-stitching on the dark color, to make it match the pattern. You don't HAVE to do the duplicate stitching, but if you don't, you'll have a bright stripe of background color in your arm pits.
Grafting directions here.
NECK AND BUTTON BAND:
These are worked in garter stitch, back and forth, on stitches picked up around the opening, all in one piece. Because it's garter stitch, it curls nicely on sloped edges:
The only place your edging won't curl is at the back of the neck, where the shoulder straps and the back-neck shaping meet; those are ninety-degree corners and not curvy at all. That's okay, we'll just do decreases there and make corners.
For the sake of clarity, I'm gonna call them 'neck corners'. You should have two on your sweater, and they should be obvious, where the nice line of the front opening goes up and whacks into the back of the neck shaping.
It is a little-known fact in the knitting world (which boggles my mind, but that's another post), that stranded knitting like this is square. That is to say, the row gauge and the stitch gauge, vertical and horizontal, are the same. In practical terms, that means there're no weirdass ratios to worry about, and we can pick up one stitch for each row or column and knit off in another direction and it will look fine. Yay.
Using whatever size needle you used for the body of your sweater, pick up the stitches. Starting at the hem on the right side (as you wear the jacket), pick up one stitch for every row of knitting. I suggest following in the line between the steek stitches and the first vertical pattern line (you can click on the photo to make it bigger):
Pick up your very first stitch in the hem fold line (purl) row. When you work around to the other side, pick up the last stitch from the hem fold line on that side, too. This will avoid any weird jog between the bottom edge of the jacket, and the bottom edge of the button band. (Whenever you're doing this kind of thing, pick up your first and last stitch as close to the bottom edge as you can; I've seen some really weird jogs on edges from doing this wrong.)
When you reach the neck corner, pick up a stitch in the vertical pattern line there, and then pick up stitches across the back of the neck, one stitch per each column of stitches. Then pick up the stitch in the vertical pattern line there, and work the rest of the way down the jacket front, picking up one stitch for each row.
Turn and knit back across. Slip the first stitch of every row. On your way back across the neck, work a 'slip one, k 2 tog, psso' in each neck corner, with the stitch from the vertical pattern line the center of the decrease. (Directions here.)
Work back and forth like this for a while, decreasing at the neck corners every other row. Stripes can be done however you want. I make it up as I go along. After two or three ridges of garter stitch (you want this edging to be about 1.5 inches/3 cm wide), work some buttonholes.
I'm not much help on buttonholes; I usually bind off three or four stitches where I want them, and then on my way back across, knitting the other direction, cast on the same number of stitches. There are much fancier buttonholes to be had out there, and if you've got a favorite, by all means, work those instead. And where you put your buttons is also a matter of taste, but on a patterned jacket like this, it may be best to line them up with the pattern; you know, one button next to each swirl. Like that.
Work a few more ridges of garter stitch. Then bind off loosely. You're done.
Next up, the hems.
Does anyone want directions on how to block this thing, or can you handle it? It's really just a soak and lay flat to dry. Let me know.