You can do that with the PIO or with APIO of the Govt. department you are questioning. In the case of all Central Government Departments, certain "post offices" have been designated as APIOs. This means that you can go to any of these post offices and submit your “fee” and “application” at the RTI counter in these post offices. They will issue you a receipt and acknowledgement and it is then the responsibility of that post office to deliver it to the right PIO.