Glue the nacells in place. Use the lines marked as guides for both sides, you may need to squeeze the tube slightly to keep it round. It is critical you glue using the line as a guide so that the vertical stabs are aligned straight with the fuselage. Note there is a left and right nacelle, the nacelle is glued even with the front of hte wing/nacelle outline, the rear must be able to clear the angled elevon, look at how they fit. Note the vertical stab slot will be angled in slightly not outward. Repeat for the other side.