Approving Request Through Web Services

I am trying to update ocmq table through Web Services.
Approving a Request ticket.
Have done following:
a) Created extaccess for ocmq table.
b) Created extaccess for Approval table.
c) Created a scenario which Reads a email and updates ocmq.

Here I get stuck. I am able to update a static field but I am not able to Approve/Reject??

What are the extra configurations required for Approving or rejecting??