Click button "Mask" on the little toolbar, you will see mask browser pane on the left. You can select a mask type from the Mask Type drop-down list. There are six built-in frame types available: Circle, Rectangle, Shadow, Text1, Text2, and Theme. Select a mask type and all the masks of this will be shown in the mask pane . Double click a mask to apply it to the current photo.

Tip: If you want to clear the mask, just directly click the button "Del Mask " on the little toolbar.