If you have to make Aadhar card or if there is a mistake in the card and want to fix it you can book an appointment online. The Unique Identification Authority of India (UIDAI) has launched Aadhaar Service Centers in many cities. These service centers will function like passport service centers. In addition to creating your new base here, you can update your name, address update, mobile number update, e-mail ID update, date of birth, gender update and biometric update (photo + fingerprint + iris).
The process of making an appointment online
                           
Within this service you can make an online appointment to get your turn in at the Aadhaar Service Center. To do this you must first go to UIDAI's website at https://uidai.gov.in/.

Here the home page will open. Place the mouse cursor on the first section in My Aadhaar and the second number below is the section, place the mouse cursor on the mouse base and click on the Book an Appointment option on the second number below.
Now the booking page will open. Select your city or location here. Now select the new page as per your requirement.

Here you have to fill in your mobile number and captcha. Then OTP will be generated.
After OTP verification, another page will be opened. There you will have to fill in the requested information and click on the NEXT button.

Then another page opens, in which you have to select the day and time to suit your needs.
The second page will show you information about your appointment. Click Submit if all the information is correct. Your appointment details will come in front of you.

IMPORTANT LINK:

Aadhaar with 125 crore people in the country According to data released by the Unique Identification Authority of India in December 2019, Aadhaar cards have been created for the 125 crore citizens living in the country. Aadhaar project was implemented in 2010 in the country.