For display settings that are specific to Online/Mobile Bidding only, go to Site Settings > Items > Catalog > Additional Online/Mobile Settings.
There you will be able to enable the button bar and specify which view of the catalog to display first (or only), and specify the wording for the screen messaging which displays during online bidding transactions:
Online/Mobile Catalog Display Settings:
Button bar settings allow you to dictate which items visitors to your site will see first - those offered via online/mobile bidding vs paper/paddle bidding at a gala or ALL. These settings also allow you to restrict visitors to a particular filtered view (eg Online/Mobile only).
You can also customize the screen messaging that displays after each action taken by bidders.