To define the criteria, you can use the Criteria and all of the Or columns of the Columns Pane.
In these cells, you should write the conditions omitting the expression itself. For example, to get the following criteria in your query:
WHERE (Field1 >= 10) AND (Field1 <= 20)
you should type ">= 10 AND <= 20" in Criteria cell of a Field1 expression.
Criteria placed in the Or columns will be grouped by columns using the AND operator and then concatenated in the WHERE (or HAVING) clause using the OR operator. For example, this visual representation will produce the following SQL statement. Please note that the criteria for Field1 are placed both to the Criteria and Or columns.
WHERE (Field1= 10) AND ((Field2 < 0) OR (Field2 > 10))
Some expressions may be of the Boolean type, for example the EXISTS clause. In this case you should type "= True" in the Criteria column of such expressions or "= False" if you want to place NOT operator before the expression.
BTW, the most common practice to learn for how to build some query is to write it once by hand and see how it will be parsed and represented visually.