The trim away the excess tissue along the ribs at each end. At the end shown the the photo I do it in two steps, cutting from the spar to the LE and then from the spar to the TE, then along the spar itself:
Go back along the edges at the LE and TE to make sure that there are no loose bits. Pushing the brush as if to try and lift the edge will reveal any loose bits and also coat them in glue:
Cut a piece of tissue large enough to cover the gap between the fourth and fifth ribs (in this example at least) Make sure that the edge on the fourth rib is nice and straight, and tack all four corners like a miniature version of how we started things for the whole wing:
Because the TE is curved at this point, cut a series of lines into the tissue 1mm or so back from he TE, this allows the tissue to conform to the curved shape.
Attach and trim as before coaxing the tissue round the coner with your finger: