Step 1:
Click on the "Seller Tools" link at the top of the page.
Step 2:
Next click on the “My Auctions” link in the dropdown menu.
Step 3:
Next, scroll to the "Upcoming" section. Locate the auction and click on "View" to open up the auction page.
Step 4:
Once the auction page is open, click on "Open for pre-bidding". After this is step is complete, your auction will be begin allowing bidders to pre-bid.