In certain templates you can change and add your own graphics.
All graphics need to be 150KB file size or less.
On each screen you can see information on the required dimensions for a graphic.
You can insert graphics will the following file formats:
jpeg
png
gif
Before you begin building your program you should find and prepare all images to the right dimensions and format, then save them all into a single folder on your computer. This will make things much easier when you come to insert them in your program.