Use google to find tutorials for knitting on two circulars. Many will be for knitting socks, but the same principles apply. I can think of two basic options: if you like to switch your two end stitches for a nice join, you will probably need to do that separately, on DPNs, magic loop, or another pair of circulars. Maybe a piece of scrap wool. Then put onto the circulars. If you don't care about that join, cast on first sleeve to on needle, put half the stitches onto other needle. Join as you like. Repeat for second sleeve. Use the tutorials.