The auction is over, something didn't sell, and now someone says they'd like to buy it.  Great!

You have (2) options.  Go to Components > Auction > Catalog tab and open the item's detail page.

1.  Change end time and enter a bid.  

Under Timing panel, change the item bid end time and click Update Item button to save change.

Then, go to the Online/Mobile tab, and click New Bid button.

Choose the item, add the bidder number or Lookup User to select, and the amount of their bid.

At the time you chose, the winner will be created and notified they won.

OR

2.  Change it to Bid Sheet/Live.  

Under Setup and Pricing panel change the Venue to Onsite and the Sale Type to Bid Sheet/Live.

Make sure you click Update Item button to save this change.

Then, go to the Bid Sheet/Live tab, and click Add Winning Bids button.

Choose the item, add the bidder number or Lookup User to select, and the amount of their winning bid.  Click Create Wins button.

The user will immediately be notified they won.