Dear Pradeep,

In order to apply for TOEFL exam you have to register.There are four possible ways for the TOEFL 2018 application, namely online, by mail, by phone and in person at the TOEFL 2018 test registration centre. 

The availability of TOEFL 2018 test dates will depend on the seat availability at the test centre. You can register for the 2018 TOEFL test online on the official website of ETS (exam conducting body). Online registration/application of TOEFL 2018 will close seven days before the test is conducted.

To know in detail you can refer below link

https://studyabroad.careers360.com/articles/toefl

Good Luck!!