May I also ask how social enterprises apply for the grant of ESR?

You may check on the website: https://www.esr.gov.hk/en/funding_application.html#docs_for_application

Great! May I also know where to get the application form?

Applicants should fill in the specified Application Form and submit it to the ESR Programs Secretariat by post/by hand or email. The address is as follows: The Secretariat to the Enhancing Self-Reliance Through District Partnership program Home Affairs Department 31/F, Southern center, 130 Hennessy Road, Wan Chai, Hong Kong (E-mail: esr_secretariat@had.gov.hk)