OK, you have the front and back on the same needle and you're ready to join to work as one piece. Take you working yarn and continue knitting front and back in the round. This will join the two pieces together from here on up to the neck.
For the sleeves, you've already done some increases by casting on sts at the ends of rows on the front and back. Join those areas together to form the sleeve opening. Then you'll pick up sts around the opening for the ribbed cuff. It's not a distinct sleeve, really just an opening with a ribbed cuff.
It is indeed a very pretty pattern.