Mind that the system refreshes every hour. It might take some time for a bidder to appear in the tool. If you can't find the new bidder neither on the Total Dashboard nor in the main menu after an hour, double check your set up.
When the bidder appeared in the system, quickly audit its performance in the Total Bidders Performance widget. Check Requests, Bid Rate, and Impressions. These metrics allow you to see if ad requests are properly sent to the bidder, how the bidder responds to these requests, and if any of ads it responded with got rendered.