You can register for CA Foundation course online at its official website icai.org. The foundation course is the first level of ICAI CA, you have to register with the Board of Studies (BOS) along with the foundation course. The last date to register for the May / June or November / December course is January 01, 2021, and July 01, 2021, respectively. First you need to register, then login and fill details in the application form, enter qualification details, upload scanned images, and and lastly pay the CA Foundation 2021 course registration fee.

For more info you can visit the following website:

https://finance.careers360.com/articles/ca-foundation-registration