​Firstly you must visit the Tax Office website using the link below in order to obtain your own personal tax number. On the main page click on 'APPLICATION FOR NON-CITIZENS' POTENTIAL TAX NUMBER' and on the following page you will be able to obtain your tax number by filling in your personal information. After filling up your application form, click on 'tamam (ok)'.

İnteraktif Vergi Dairesi (gib.gov.tr)

-What can i do with my tax number?

After completing your residence permit application form, one of your required documents is proof of tax payment. The only way you can make your tax payment is by using your tax number.

-How can i use my tax number to pay for the tax fee as part of my residence permit application?

There are two ways you can use your tax number to pay for your tax fee: you can either pay on the same website online, or you can visit the nearest tax office (vergi dairesi) and provide your tax number to complete the payment.
The closest tax offıce to the İstanbul Aydın University Campus is Avcılar Vergi Dairesi (AVCILAR VERGİ DAİRESİ MÜDÜRLÜĞÜ - Google Haritalar)

NOTE: You can only obtain the tax number through the website.