The normal car radios have the left and right 2 holes in which you can introduce this release key to unlock the old radio and remove then. There are also many other methods, for example with thin nails or take Schaschlykspieße metal. The problem with these variations is then only, does not always lead to the desired success. Thus prefer to buy the right accessories and you're on the safe route.
The handle is actually very simple, you put 1 release key on the left and the other. Right in the holes of the radio One then feels the resistance and to the extent the release key should be pushed. Then you can easily push outward. Now you realize how the retaining springs on the radio to move and the radio is unlocked. You can pull the radio out of the slot draw with a slow now and that was about it.
I must admit, I tried it out first with nails and wanted to save the nearly 3 euros. but then lacking the right grip, you have here with this release key. They are as described above, as a U bent and so you have a better "grip" which is important later when pushing. The release key is an accessory, which is now not used very often, but maybe you can then continue to borrow in the acquaintance / relationship if someone even buy a new radio.
My conclusion is at least: Better to have spend 3 Euro and buy the right accessories, instead try other means to get to the desired success. The price - / performance ratio I step here as very good and can also recommend the release key.