Everything Sue said is good, but I just thought I would add a little more that might help you. I recently did a sweater that is built like this and even though I am experienced I still messed up on my first try with the first sleeve and had to do it again.
The stitches that you left on holders on the body of the sweater and the ones on holders for the sleeve are the armpits. :lol: It helps if you put them together and try to situate the sleeve so that it looks like it is coming out of the sweater like a sleeve ought to. Then do like Sue said and knit the stitches off the dpns onto the body of the sweater so that the sleeve will end up where it should be.
Sue answered about the stitches on the holders, you leave them for now and deal with them later. Maybe after you get the sleeves attached you will be able to figure out where the 2 stitches came from and make appropriate adjustments to compensate for them.
Good luck. If it's like mine the first number of rounds may be awkward to do, but hang in there it gets easier as you get a ways pass the joining of the sleeves. Mine was a cardigan instead of a pullover, but used this same construction technique.