The right side display (where this help is now) will show the database name you've selected, the SMILES representing the structure you've drawn, a link to view the SQL executed to retrieve the similar structures from the database, and the number of hits found with an option to download a SMILES file of these. Below that is shown a list of SMILES that represent structures found in the database search that are similar to the structure you have drawn. Running the mouse over each SMILES will show the structure (on the left below the editor) represented by that SMILES with any possible substructure highlighted in red. Clicking on a SMILES will bring the structure into the editor, where you can modify it, or simply search again using the new structure. The percent similarity is also displayed for each structure found. The list of numbers after each SMILES are the atom numbers corresponding to any substructure found in each SMILES. Note that your search structure may be very similar to the a compound, yet not be an exact substructure.
Here is a sample output.
Search of nci.structure for CNC(=O)Cc1ccccc1 [See SQL]