Click on the button to view a list of available options for the field.
Navigate to the record you wish to select using your mouse, or using the keyboard arrow keys.
Double click on the record you wish to select, or click the button.
You can sort any of the columns in the grid to make searching easier by clicking in the header row. For example click on "Name" to sort the grid alphabetically by Account Name and click on "Name" again to sort in reverse order.