Procedure for registration of Digital Signature Certificate and upload of Income Tax Return

I am trying to file Income Tax return (ITR 6) of a company. Do I have to use a Digital Signature? Is this mandatory only for domestic companies- are there any exceptions? What type of Digital signature should I use? Should the Digital Signature (DSC) be in the name of the Company or the Director? Do I have to register the DSC prior to uploading the ITR of the Company?