The Scene is initially empty and you start with creating a schema on it:
A schema is a visual representation of the query that would be used to analyze a nucleotide sequence. It consists of elements.
An element of a schema. There are two types of elements: algorithm elements and constraint elements.
An element of a schema that represents an algorithm used to analyze a nucleotide sequence.
An element of a schema used to impose constraints on the results obtained from algorithm elements.
Your first step is to add necessary algorithm elements to the Scene by dragging them to the Palette.
The next step is to add constraints on the algorithms results.