When doing this repair that digi flex can be tricky. Seat the screen at the top first and then flip it around so that the bottom is lifted enough to fit a spudger between the frame and the digi. Press inward on the digi flex to train it to bend the correct direction and Viola! a properly installed digi. Let us know how that worked for you!
I have to apologize. For some reason I thought you were talking about an iPad mini. For the iPad air I would lay the iPad flat and stand the replacement up at a 90 degree angle along the side of the iPad where the cabling goes through. This will help make sure you cable go into the chasis of the ipad. Then, close it like a book keeping slight pressure on the cable edge so that the cables seat properly.