I made a baby sweater once that I used steeks on. I put sleeves on it but it is the same idea. You need the steek at the armhole so that you can knit continuously around right over what will become the armhole and have the steek to cut to make the hole later. Here is a link to the project page of the little sweater I made at Ravelry. The third picture down will show you what it is going to look like when you have the steek in for the armhole. LINK
To help you picture what is going on....You are knitting in a continuous circle and you need a steek wherever there will be an opening, i.e. for the front of the cardigan and for each sleeve. Then later you cut all the steeks. Then you will have to join the shoulder seams and I think from looking at your picture you will pick up stitches around the armholes and knit little bands of corrugated ribbing around them. You also pick up stitches around the neck and for front bands and knit the same type of bands you do on the sleeve openings.
With color Blush, k5 steek sts., k 45 Front 1 sts., put 20 sts. on holder, CO 9 armhole steek sts., K 93 Upper Back sts., put 20 sts. on holder, CO 9 armhole steek sts., K 45 Front 2 sts., k 4 steek sts.
Since it is sleeveless I'm not sure why I need steeks there!
So the 20 on each arm area are on the holders and then I have the 9 steek stitches on each side on the needle.
So you are making a steek in the front and at each armhole that has 9 stitches in each steek. Those first directions start you at the beginning of a round and you k5 (about 1/2 of the the steek since it is 9 stitches) steek sts (the center front steek), then k 45 for the one front, put 20 on a holder (this large number is because you are using a fine yarn, and it takes that many for the underarm they want). Then you CO 9 altogether for the steek under that arm (this will be your bridge across what will become the armhole). Then you K the 93 in the back and then you are at the other armhole. So again you put 20 on a holder and again you cast on 9 for the steek so you can keep working in the round right over what will be the armhole. Then you k 45 for the other front and the 4 remaining stitches of the center front steek.
My question is that since I am holding 20 sts. on each side and had to cast on ONLY 9 sts. in their place my design is going to be "off". Am I not getting this??
Here is where you need to read your pattern chart and compare it to what you have knit below to see where you are on the chart and put the stitches that need to go next. You are leaving out those 20 but you should be able to look at where you are in the pattern and pick it up there.
I also have to make decreases and hope I can do those right.
You make the decreases just like any decreases but make them just in from the steek (not in the steek). You might like to place them a stitch or 2 in from the steek wherever you have to decrease for shaping.
Ingrid has a sticky thread about steeking on the list page for the "how-to question" section. I suggest you read through everything there. Time consuming but enlightening. Ingrid will also answer questions about steeking if left in that thread. She helped me with mine. :muah: