Making an grouped shape have a transparant section

[coleman cox]

greetings, first time poster here. new to the community and to Affinity. I am trying to recreate a graphic with a transparent background like I made with another program but struggling to make it right. I am creating a lock and trying to add a created keyhole I made from grouped shapes. I want the key hole to show up as transparent, not white so that when I save the entire project with a transparent background, the key hole will be transparent as well. Is there a way to do this, or a way to erase the keyhole shaped section of the opaque lock?  the attached document is what I am trying to reproduce here so that it is higher resolution than the png file.

[toltec]

It would be very helpful to know what software you are using ?

 

In Photo, combine the keyhole shapes by selecting both objects and going Layer > Geometry  > Add. Put the keyhole on top of the lock body, select both layers and go Layer > Geometry > Subtract. 

 

Result, an 'ole.