Zoom out in the picture you want so that fits in the screen with nothing else showing in the image, the numbers etc. Then press Print screen on the top row of your keyboard. You can then open it in a photo editing programme, crop off all the unwanted part of the screen image, increase the picture to the size you want and save to your computer. I have done about forty of the pictures this way.
If you don't have an image editing programme, download Irfanview, it is free and will do the job very well.
Jebber