There are two ways you can delete a note.

Hold drag and delete
Click-and-hold or touch-and-hold on your note. A trash can will appear bottom right of your screen. Drag your note over the trash can and let go. Your note will be deleted.

Double click or tap for the Edit Panel
Double-tap or double-click your note to open its Edit Panel. On the left-hand side of the Edit Panel you will see a trash can. Click this and the note will be deleted.

Want to delete several notes at once?

Create a temporary Group [How do I create a Group?] around the notes that you wish to delete. Then drag the group and all its contents to the trash can at the bottom right of your screen.