Yes, you can import a graphic into a blank template; however, the quality of the poster is going to depend on a combination of the height, width, and resolution of your original image. If your height and width are greater than 2400 x 3600, and your resolution is 150 dpi or higher, you are safe for a good print. There are several resources available on the internet to help understand print quality when enlarging photos. Please see previous question for a list of supported graphic file formats.