How could I get the form of declaration of lieu obc for uploading in her advance registration process. Please explain step by step.

During step 1 in uploading obc Certificate for registration of JEE advance I chose option for uploading the obc Certificate on 26/09/2020. In step 2 it's asking to upload declaration of lieu obc Certificate. Tell me how I'll get form for uploading declaration of lieu. Plzzzz explain in detail.