Buyers can perform both trading actions in the "Buyer Actions" area. On the left side of the area, buyers input bids in the price box and click the "Bid" button to submit.
On the right side of the area, buyers can buy at the current lowest ask price by clicking the "Buy" button.
During some trading periods, the minimum bid price and the maximum bid price may be specified on the top of the "Buyer Actions" area. For example, if the minimum bid price were set at $5.00, then all bids would have to be $5.00 or more.
Also, during some trading periods, there may be a per-unit tax imposed. If a tax is imposed, the amount will be noted on the top of the "Buyer Actions" area. The tax will be taken out the buyer's profits.