Photoshop: Susan Boyle/50 Cent

I have been tasked with producing a piece of Photoshop work where I have to combine Susan Boyle and 50 Cent together in one image. I have not used Photoshop before however, to create the image i just used the "Lasso Tool" to crop out bits of both images and then just placed the second image in the place of the cropped area of the first image. I have not tested out many other tools within Photoshop but hopefully the more I use it the better I will get.