There is no exact spor for the wing. Finish the whole plane accept wing mounting. Once complete, make a mark on the wing for the CG (most say about 9.5" back from leading edge, slide the wings on, place plane on balancer at CG marks, and now use the sliding wing to balance the plane. Once balanced, make marks and drill and install the blind nuts.

BTW, the front blind nuts are a PITA (pain in the ass) to install. I made a little tool from aluminum shaped like an "L" to install them. You may also want to add a little CA to keep them in place. Mine popped out several times at the field before I got smart and glued them.