From the bid page, click the bid you wish to counter then click the "Counter" icon. From the bid comparison screen, you will click on "Counter" from the "Actions" drop-down of the bid you wish to counter. On the countering page, you will have the option to adjust the original Percent of Value, Recourse, Closing Date, and Loans selected for the bid. Additional notes can be added to your counter in the available text box.
Once you've entered your adjusted terms, click "Submit Counter," and a notification of a counter will be sent to the receiving party.