You will be able to build your expression by adding items to the empty window on top of the screen. You can choose from the row of standard operator buttons (such as +, -, =, And, Or, etc.) immediately below that window. The real power of Expression Builder, however, lies in the bottom portion of the screen -- the expression elements.
Choose an expression element by expanding the folders in the leftmost portion of the expression elements section and then choosing specific elements in the two right windows. For example, if you'd like to count all of the rows in a table that have a value of "red" for the attribute "Apple", begin by expanding the Functions folder. Then select Built-In Functions in the expanded Functions folder. This is shown in the illustration above