To obtain an apostille, you must first obtain an original diploma or ÖSYM certificate. Once you have that document, you can apply for an Apostille.
First, you must get your original diploma or certificate translated by an official translator who is a Turkish citizen and a holder of a state-granted license. Then you need to notarize the document with a notary.
Finally, you must go to the competent authority and ask Apostille in Turkey them to make an Apostille. Make sure that the person who is doing the translating is a licensed translator and that the notarizing is done by a properly trained notary.
If you do not follow these steps correctly, the Apostille you receive may be invalid. It is important to keep the original document safe. If you lose the document, you may be unable to obtain a valid Apostille. It is possible to have your passport updated.