Submitting :post request through etrade api

[akat711]

The provided examples work great, but I noticed there is no example for submitting a post request which is needed to create a trade order. My call:
response = consumer.request(:post, "https://etwssandbox.etrade.com/order/sandbox/rest/previewequityorder", access_token,{}, {}, { 'Content-Type' => 'application/xml', :xml => myxmlorder} )

The question is how can i send the xml bearing the order in the call? Thanks very much.