How do you measure anti-dna antibody bu using ELISA?

The antigen that is to be measured is applied to a surface and an antibody is attached to it. The antibody has has an enzyme added that absorbs light. The antibody attaches to the antigen. A fluorescent light is shone on the antigen-antibody and it glows wherever antibody has bound itself to an antigen. This way the antigen shows clearly and can be measured.