So this is right at the beginning of the sweater beginning at the cast on and working down? The two circulars should work. Let me try to explain what to do.
I'd begin by casting on all your stitches onto one of the needles. Then transfer about half of them (if it is ribbing I like to have the first stitch on the second needle be a knit stitch, not absolutely necessary, but I like it better). Now hold the two needles so that the cast on stitches form a circle (you can lay this out on a table if this helps you) and turn things until you have the working yarn coming from the needle on the right. Move the stitches on the right needle near the end of the needle with the yarn coming from it. Move the stitches on the other needle (hold this needle in your left hand) up near the end of the needle so that they are near the working yarn on the right needle.
You are going to be knitting off of the needle on your left, so take the free end of that same needle in your right hand to work with. (This is the main thing to remember- always knit the stitches on either needle with the needle the stitches sit on.) At this point I like to pull the needle on the right up so that the stitches there are no longer near the needle tip, but you want to keep the stitches themselves and the working yarn near needle in your left hand. Knit the first stitch pulling the two needles close to each other as you do. Place a marker to mark the beginning of the round. Continue to work across that needle until you have gotten to its end. When you have knitted the last stitch, pull that needle up so that the stitches cannot fall off of that end of the needle. (so all the stitches are on the cable part of the needle)
Now drop that first needle entirely and take the other needle in your hands. (If your needles are the same color/kind, so that they are identical, always take a few extra seconds at the needle changes to make sure you have both ends of the same needle in your hands to begin the next part. You need to do this anyway, but spend a little more time if the needles are identical.)
I know this can be a little tricky to figure out. But if you take a minute to think, there is only one real option of what to do that will allow you to continue working around the circle.
**Pull on one end of the new needle until the stitches that need to be worked next are brought to the working end of the needle, up near the working yarn. Take a hold on that needle end with your left hand (this will be your new holding needle) Take the other end of the same needle
in your right hand. Pull that needle end up so that you can use it to knit with. Knit the first stitch drawing the two needles as close to each other as you can on that stitch. Continue across the needle. When you've knit them all, pull the needle up so the stitches are on the cable. ) Now go back to where I put the ** and repeat.
You might try doing this while a friend reads the directions to you so you can keep your eyes on the knitting and not be trying to shift from the instructions to the knitting.
I hope this helps. If not get back and we'll try other options. This is tricky at first, but not hard once you see what is happening. You will be able to work the whole sweater on the two needles if you want, or can switch to just one when there are enough stitches to reach comfortably around one needle.
To make the switch to one needle, begin a round the usual way. When you get to the end of that needle instead of doing anything with the second needle, just keep knitting around with the first needle until all the stitches are on one needle.