If your live auction is set as 'catalogue' mode, this means your item settings are probably set as Visible to guests with bidding Disabled.
To enter live auction winners, hide the items from the guests' phone and enable bidding in the item list view (the three bar button on the top right corner while you're on the live auction page).
Now go to each item, click 'Place Bid', search for the guest who won the item, and enter the winning amount.
Once you have completed this step for all live auction items, navigate back to the list view, select all items, and Close the items. This action moves the items to the respective guests' bills.