How do I get the Tax Exemption Certificate in India by myself without having to go to a service provider?

I am planning on returning to India this year. I was told that I will have to submit the Tax Exemption Certificate to my employer to avoid being taxed for the income I was paid while in the US.
I would like to know the process to obtain the tax exemption certificate.
I would like to know the process to obtain the tax exemption certificate.