How can I get study visa for UK and who will provide Agent or University?

If you are applying for student visa for UK, then you should have CAS (confirmation of acceptance of studies)

You must apply online for a Student visa. Details of the documents required can be found on https://www.gov.uk/student-visa/documents-you-must-provide

When you make submit an online application, you will receive an email confirming details of your appointment.

Everyone has to attend the interview after submitting the online application. It is to ensure to judge the intention to student.

You’ll get a letter or an email with the result of your application. It will explain what you need to do next.

It is issued by UK Visas and Immigration (UKVI) which is responsible for Home Office responsible for the United Kingdom's visa system.