Draw molecule then push SMILES Button.
Push mouse button and Drag (keep push). Up mouse button, then one bond appear. Point edge of bond by mouse,Blue circle appear. At there push mouse button and Drag again. If you want to make double or triple bond, select one atom (Blue circle appear), push mouse button and keep drag to other atom (Blue circle appear), then up mouse button. You need not draw hydrogen. If you want to change atom type Carbon to Oxygen, Sulfur, or Nitrogen. Please select Atom type radio button. And select atom type then point out one Atom which you want to change.

You can select and copy SMILES(Ctr+C or Command+C)