Find the 4 front wing triangle sections, gluing 2 of them together to make the 2 front wing sections.
Slide the fuselage Battery tray onto the spline, all the way to where the notch in the spline rests against the F4 former. See pic. Do this on a flat surface, propping up the fuselage so that the fuse is perfectly in line with the wing both up and down, and side to side, and centered at the wing joint and spline. When satisfied with the placement, back the fuse off, apply glue to spline, and reposition and let glue dry. USE a SLOW drying glue or 5 minute epoxy for this joint so you have some working time to position the fuselage and wing to make the joint lined up well.