Procedure for Voluntary Provident Fund (VPF) from the employer's side

One of our clients registered voluntarily for EPFO. One of the employees wants to opt for VPF. Can they accept the request? Is there any application, form, or declaration from the employee required? Also, is there any procedure to be followed by the employer?

Please suggest.

Thank you in advance.

If you want the correct answer, please post with all background details and conditions/circumstances. Else, people will make the wrong assumptions, and you will get a wrong or suboptimal solution. The above details are incomplete. Please explain what the designation, salary, etc., of the person not wanting to join the PF scheme are and the reason (if any).