The advice to separate images from the internet and my own images with different folders will be useful because it will stop me from getting things mixed up. The process of inserting images onto a Photoshop document is simple because you just import whatever you want from your documents. I now know that if there is a little symbol in the corner of the layer box for the image, you need to right click it and select rasterize so that you can edit it. I also found changing the size of images to be easy by clicking on free transform or CTRL+T.
Photoshop 4 Inserting Images