Daneccleston86

Afternoon everyone, I have just bought Affinity Photo (love it so far) but just need some guidance on such a simple thing, I am trying to quickly remove backgrounds from photos to create pngs so i can make it look like my nephew is being chased by a T Rex... I can select the area okay using the magic wand / smart tools but how do I then delete the area that is selected?!?! I have tried changing the mode to Subtract but on selection it does nothing at all... Any help would be great Cheers Dan