Next up is to remove the transponder from the donor key. *If your car does not use a transponder you can skip this step.* It is recommended to use the valet key, but you can also use one of the standard keys. Here are photos of the 2011 WRX valet key getting opened up.
On the 2011 WRX you slice the rubber open, and then there will be a white platic section around the metal key. This pops apart and the transponder comes out. If the car uses a transponder, you will need the transponder in the new key to be able to start the car. The process may vary slightly on other model years that use a transponder.
On the flip shell there is a little spot for it next to the pivot mechanism. The transponder does not stay in place by simply setting it in the slot and assembling the flip key. You will need to use a dab of hot glue or adhesive to hold it in place.
You'll then want to place the remote module from the Legacy key into the flip housing. It should just sit into place. Make sure to flip the key over and make sure all the buttons are showing through properly. It can take some wiggling to get the remote to sit correctly. When it is properly installed all of the buttons should be able to be pressed.
After that, slide the button into the pivot mechanism. There are 3 prongs on the button, and 1 of them is smaller. If you look into the pivot piece, you should be able to see where the smaller prong will sit. Slide it into place. Then set the button/pivot into the housing.
Next you'll need to insert the spring into the button. You want to insert the end of the spring with the end of the last coil bent inwards. If you look at the inside of the button you will see there is a slot for this part of the spring to sit into. Make sure it sits into this slot. When it is in place you should be able to twist the spring and feel the blade turn. If the spring spins freely, then it is not seated correctly.
Once the spring is in place, you need to get the housing back together. This seems simple, except you need to preload the spring or the blade won't pop open. The other side of the housing has some grooves/tabs that will hold the other side of the spring (the end sticks outwards). Line up the housing like the photo above and make sure the spring seats into one of the slots, then give the housing a full turn counter clockwise, and the close the housing. This preloads the spring and makes it pop open with good force.
After the housing is all closed up, you need to screw it together. Use a small (size 0) screwdriver to do this. The screw will self tap into the plastic. Do not overtighten them or they will strip out. Flip the key in and out to make sure it works. Then add the sticker, and you're done with assembly!