What I will be demonstrating in this tutorial is how to crop a image. Very basic tool for you to keep in mind when working with photos. All we have to do basically is grab the main attention out of the image and display it in a more wider position.
Go outside with friends or family and take a few random pictures to work with. Or if you don't have any at the moment, just take the one provided above. You want a image that has a lot of attention going towards one figure like the skateboarder in this picture.
Let's start off by grabbing your Rectangular Marquee Selection tool in the top left of your toolbox. Simply select a small portion of what you want to be displayed more than the rest of the picture. Mine is obviously the skateboarder, we don't want to see the crowd!
Once you have selected around the part of the image you want to keep, hit Ctrl+C to copy. Now go to File > New on the top. It will automatically put it in the right measurements if you copied correctly.
Now since you have a brand new canvas, hit Ctrl+V to paste the copied document you had in before. Now all the rest of the image should be cutout besides the main part. Again, this is a very basic tutorial for beginners at Photoshop.