How can i done income tax registration

hello to all memebers.

we are chandigarh based patnership firm. we have pan card on name of our firm. i want to apply for income tax registration. Can anybody please guide me. 

Reason why I need it.

I want to apply for payment gateway for my website . Payment gateway service providers require this document from me.

They told clear visible copy of income tax registration

Anybody can guide. it will be very helpfull

Thanks