How to change custom authorizer to type request

i am using a custom authorizer with type TOKEN now but I am unable to access all the data in headers sent from client side. on reading further, I concluded that the custom authorizer needs to be of type:REQUEST if i want to access the headers and other parameters too.
now, I have been trying to find some info regarding changing the type of custom authorizer to ‘request’ but still not sure how to do this.
could anyone here explain how to do that?