Once you have found a wine on ShareWine that you find interesting, you can place a bid.
To place a bid, follow these steps:
Step 1: Click on the ad you would like to bid on.
Step 2: The ad shows what the current price is.
Step 3: You can choose to place a bid and click on the amount you want to place.
Step 4: Finally, press the green button, with the words: "Submit Bid". 
This can also be done automatically in which you place a max bid. This means that ShareWine's system automatically bids on your behalf until your max bid is reached. Read more about maximum bids here.
Remember to follow the ad to be sure that you have the highest bid! Read how to follow an ad here.