If you’re new to Photoshop, and you’ve been using another graphics program (e.g. Paint Shop Pro) for a long time, then even something as simple as copying and pasting can appear quite confusing at first! So I wrote a quick tutorial on it.
Open up your image, and go to Select > All. This should make an animated dotted line appear around the outside of your image (don’t worry it’s not permanent!)
Then press Ctrl and C. This will copy the image. To paste, open up a new image, then press Ctrl and V to paste. If you paste straight away, it will create a new layer on your previous image. You need to open a new image and paste on to that.
Press Ctrl and D together to deselect the original image, and the dotted line will be removed.
If you’re pasting from another graphics program or the Internet, copy your image, then open a new image in Photoshop and press Ctrl and V.