I wasn't sure if you meant to cut, copy, crop or delete.

basically if you don't have the picture on your computer now you could copy the one you want to change.

right click on it and it should have the option of something like "save image as" - there are others but that is the one I use.

when you click that one make sure it goes to a place where you can find it - I send mine to My pictures folder.

then go to the picture and play around with editing it for size , making more copies, cropping, etc-
right click and go to "open with" - there should be a few options to open it with if you have a few programs for image editing- try them to see which one you like best.