YEah, do mckinleys tutorial or, the way you do that is, you select the end isopram you want to attatch, offset the curve, projecto it onto the sureface you want to attatch it to, trim that surface along the curve you projected onto it, then perform a freeform fillet between the two surfaces using the end isopram of the surface you want to attatch and the trim edge of the surface trim you just did.